The National Union of Teachers says there is no evidence to show academy status will improve schools more rapidly than local authority schools.

The union's conference has backed a strike ballot for this summer term.

The Department for Education says the union was "playing politics with our children's future".

And the Education Secretary Nicky Morgan has told teachers she has no intention of backing down, warning another teachers' union, the NASUWT, that there is no "reverse gear" on the proposed reforms.

Mrs Morgan was heckled and faced shouts of "rubbish" from delegates during her speech arguing that the compulsory academy policy would raise standards.

Analysis from the NUT conference, Brighton

The National Union of Teachers is no stranger to challenging government education policies - and a call for strike action might also have been as predictable as bad weather over a bank holiday weekend.

But on the issue of the government forcing all schools to become academies, regardless of the views of parents, the NUT clearly feels it is tapping into a much wider sense of unease.

The union's leadership thinks the government has wrong-footed itself over this, antagonising grassroots Conservatives and Liberal Democrats, as well as its more traditional left-wing supporters.

Town hall Tories are a much trickier target for the government than what they would see as conference hall Trots. And there are murmurings of concern about what academy chains would mean for village schools and faith schools.

The element of compulsion could aggravate parents and there might be difficult questions about the merits of successful local schools being handed over to an unfamiliar academy chain.

During the debate over a strike ballot on the academy plans, there was a distinct absence of tub-thumping and rhetoric that might have been expected. Did they have a more steely sense of getting a result?

The NUT annual conference in Brighton has supported calls for a sustained campaign against compelling schools to be academies, including a ballot for a one-day strike.

The union's treasurer Ian Murch said it would see schools being "stolen" from local communities by "arrogant ministers".

He challenged the handing over of schools to academy chains, saying that it would be a step towards privatisation.

Mr Murch said schools should be seen as a "public service and not a business opportunity"

Hazel Danson from the union's executive said the policy of making all schools academies would cause "absolute chaos" at a time when there were more pressing priorities such as teacher shortages.

She said the plans would "remove parental voice as well as parental choice".

The NUT wants to build a wider coalition of opposition to the academy policy.

Alex Kenny, from the union's executive, told the conference that the government had over-reached itself - and opposition now stretched from "Mumsnet to the Financial Times".

A number of Conservative party representatives in local government have spoken out against the plans which would remove the role of local councils.

Liberal Democrat leader Tim Farron has said the compulsory academy plan is "worse than misguided - it is downright harmful. It will be a costly and disruptive process for thousands of schools".

The cross-party Local Government Association has spoken out strongly against the plans, saying that it "defies reason" to claim that local authority schools are performing less well than academies.

"Forcing schools to become academies strips parents, teachers and faith groups of any local choice," said an LGA statement.

And it says the academy plans cannot be considered an "appropriate use of public money".

Labour leader Jeremy Corbyn told the NUT conference that compulsory academy status was a step towards "asset stripping" the state education system.

The NUT conference heard calls for industrial action in opposition to the changes, which union leaders say could threaten teachers' pay and job security, as such decisions about pay and conditions would be decided by academy chains.

They accuse the plans of being undemocratic and "evidence free".

The union's deputy leader, Kevin Courtney, has described it as a non-manifesto policy which had been "written on the back of a fag packet".

The union has written to Mrs Morgan calling on her to provide evidence that academies were likely to improve more rapidly than local authority schools.

But the education secretary has made clear that she will not retreat on the policy.

She says that there is international evidence to show that more autonomy for schools helps to raise standards.

And she says that an all-academy system will give greater power to high-achieving head teachers.

A Department for Education spokeswoman said: "It's disappointing that the NUT would rather play politics with our children's future than work constructively with us to deliver our vision for educational excellence everywhere.

"We make no apology for our reforms, which have resulted in a record number of children now being taught in good or outstanding schools - 1.4 million more than in 2010.

"And as set out in our White Paper we are determined to continue with our vision to ensure every single child has the best possible education, as well as raising the status of the profession. It would be refreshing to see the NUT doing likewise."

Adults paid sixpence and the under-12s got in for half-price. Queues spilled into the grounds of Crystal Palace in autumn 1871 as the public waited for a glimpse of the biggest sensation in London.

It wasn't a freak show or a demonstration of the latest technology that attracted them, but a creature that had been around for millions of years, living in every ocean.

An advertisement in the Times informed potential visitors to Crystal Palace's new aquarium the chance to view "thousands of living creatures of the sea", but what everyone wanted to see was "the wonderful Octopus, or Devil Fish".

The eight-legged, boneless cephalopod mollusc (not a fish) had become a literary sensation, with the publication of Victor Hugo's novel Toilers of the Sea five years earlier. It featured a fight between a fisherman and a giant octopus. Hugo claimed the animal, well known previously to seafarers but little seen by anyone else, drank the blood of its "victims".

"He draws you to him, and into himself," he wrote. "While bound down, glued to the ground, you feel yourself gradually emptied into this horrible pouch, which is the monster itself."

In 1867, a year after the publication of Toilers of the Sea, a captive octopus went on display at the aquarium in the French town of Boulogne. The Crystal Palace aquarium put one on display when it opened in 1871.

It "had to bear the uninterrupted gaze of on-lookers", according to JE Taylor, a noted Victorian writer on aquarium-related matters. "It sat for its portrait in the illustrated papers, and had all its points noted down by newspaper correspondents with the same faithful detail as if they were those of prize cattle at the Agricultural Show."

When another aquarium opened in Brighton in 1872, the presence of an octopus - the craze for which was becoming known as "cephalomania" - was de rigeur. The owners added to any Hugo-inspired sense of seaside terror by informing customers it had been "caught in a lobster-pot at Eastbourne".

"It would have been a bit like a freak show for the Victorians," says Carey Duckhouse, curator of the Brighton Sea Life Centre, as the aquarium is known today. "They would have featured models of ships in the cases for the octopus to grab hold of. They would probably have loved that, as they enjoy playing."

One possible visitor to Crystal Palace aquarium was the writer HG Wells, who was just five years old when it opened and lived in Bromley, four miles away. Several octopus-like creatures appear in his stories.

In his 1894 essay The Extinction of Man, Wells pondered a "new and larger variety" that might "acquire a preferential taste for human nutriment". Could it, he asked, start "picking the sailors off a stranded ship" and eventually "batten on" visitors to the seaside?

More famously, the invading Martians in Wells's War of the Worlds have tentacle-like arms. "To me it is quite credible that the Martians may be descended from beings not unlike ourselves," the narrator relates, "by a gradual development of brain and hands (the latter giving rise to the two bunches of delicate tentacles at last) at the expense of the rest of the body. Without the body the brain would, of course, become a mere selfish intelligence, without any of the emotional substratum of the human being."

Octopuses, solitary creatures which live in dens, have hard, parrot-like beaks for killing, and tearing pieces of flesh from their prey. They pierce the shells of their prey, injecting poison that causes paralysis. They then release salivary enzymes, loosening the meat from the inner shell.

The HG Wells Society says there is no "compelling evidence" that Wells went to see the Crystal Palace octopus, but doesn't discount the idea. He wrote of seeing the dinosaur statues in the same park, the world's first attempt to create life-sized models of the ancient animals.

Cephalomania would have been hard for Wells to avoid growing up. A giant squid, related to the octopus, appeared in Jules Verne's 1869 novel 20,000 Leagues Under the Sea, subsequently made into several films.

Tentacles have continued to be synonymous with creepiness and oddness. Cthulhu, a cosmic deity featured in the 1928 HP Lovecraft story Call of Cthulhu, has an octopus-like head. One of Spider-Man's enemies is Dr Octopus, a scientist who has designed four metallic tentacles to complement his arms and legs.

Research published last year showed that, so long ago was its genetic diversion from other creatures, that the octopus effectively had "the first sequenced genome from an alien".

The Crystal Palace octopus and its successors remained on display until the 1890s, when a monkey house replaced the aquarium. Attitudes appeared to soften during that period - the unfathomable moving to the outer realms of the edible.

"The octopus is highly valued as a bait for catching other fish," Andrew Tuer wrote to the Times in 1887, "but, while beloved of the Spanish and other seamen, it is not often eaten in this country. I had one curried and found it most excellent - something like tender tripe."

When Pink Floyd headlined The Garden Party concert at Crystal Palace in 1971, a century after the aquarium had opened, their performance included a large inflatable octopus. It floated on the lake in front of the stage, surrounded by dry ice - a scene Wells might have enjoyed.

In 2010, Paul, an octopus living at the Sea Life Centre in Oberhausen, Germany, was credited with correctly predicting eight results in a row. Was he using his "alien" powers to help humanity, or at least the part of it that liked a flutter, the press wondered. Statistical experts put his oracle-like qualities down to good luck.

Ironically, one of the ongoing attractions of the "alien" octopus is the ability to behave in what's seen as a "human-like" way, says Duckhouse. They can open jars and grab their handlers as they pass by open-topped tanks, looking for attention.

"They've got personality," says Duckhouse. "They would have seemed outrageous to the Victorians, but they are better understood today and people love them."

Some 1,500 officers have been deployed to the Olympic Stadium area, authorities have said.

Officials are in high alert following Tuesday's attacks in Brussels.

Last year, a friendly between Germany and the Netherlands in Hannover was called off two hours before its start due to a security threat, four days after the Paris attacks.

One of the targets in Paris was the Stade de France, where Germany were playingFrance in a friendly match.

Some 72,000 people are expected to attend Saturday's match in Berlin between two of the favourites for June's Euro 2016.

In the hours ahead of the game, fans gathered around the stadium amid a heavy security presence.

They face security checks and bag searches before entering the arena.

"This is of course a very large event drawing lots of people. Like all large events, there is a certain risk involved, so we are well prepared," Berlin police spokesman Stefan Redlich told Reuters news agency.

"We searched the Olympic stadium with dogs trained to sniff out explosives before we let the fans in. So we can be relatively certain that there are no dangerous objects in the stadium."