The biggest day of strikes in over a decade caused major disruption in London on Wednesday as teachers, train drivers, bus drivers, lecturers and civil servants walked out.

More than 500,000 workers belonging to seven unions were taking part in “walkout Wednesday” — with little sign of an end to the strikes or the Government backing down. An estimated 250,000 London pupils were stuck at home because their schools were shut.

A further 500,000 were affected because their schools were partially closed, according to Evening Standard analysis. London was expected to be the worst hit area in Britain, with 23 per cent of schools closing completely and 45 per cent partially closed. Some parents only found out this morning whether their children would have to stay at home.

Education Secretary Gillian Keegan branded teachers who failed to notify headteachers of their intention not to turn up for work as “unreasonable” and insisted: “We cannot give inflation-busting pay rises.”

But Dr Mary Bousted, general secretary of the National Education Union, said a “toxic combination” of low wages and high workload was forcing teachers to quit. “We have teachers who are worried about whether they can put petrol in their cars to drive to work,” she said.

She said 85 per cent of schools across the country were fully or partially closed “for a strike that didn’t need to happen if the Government had been prepared to negotiate”. Some teachers were having to take second jobs to make ends meet, she added.

Ms Keegan dismissed suggestions that some teachers were regularly using food banks as “not credible”.

The Education Secretary said: “What we cannot do is give inflation-busting pay rises to one part of the workforce and make inflation worse for everybody. That’s not an economically sensible thing to do.”

Health chiefs feared “sudden no shows” at hospitals and GP surgeries from parents who discovered on Wednesday morning that their child’s school was closed.

Only about a third of trains were running, with rail commuters heading into the capital only able to rely on the Elizabeth line — which on Wednesday hit 100 million passenger journeys since opening last May — the Underground, London Overground and South Western Railway.

There were no Thameslink, Southern, Great Northern, Avanti West Coast, Heathrow Express, Gatwick Express or Southeastern services. London North Eastern Railway, Great Western Railway and Greater Anglia were running a skeleton service, though Greater Anglia asked passengers to “avoid travelling with us”.

Aslef general secretary Mick Whelan, speaking from a picket line outside Euston station, said strikes by train drivers would continue for the “very long haul” if an improved pay offer was not made. There will be a further 24-hour train strike on Friday, and services tomorrow and on Saturday will start later than normal.

Angie Doll, of Govia Thameslink Railway, said: “These strikes are terrible for everyone and we hope the national negotiations come to a successful resolution soon.”

The Rail Delivery Group, which represents the train firms, said: “Having made an initial offer which would have taken average driver salaries from £60,000 to nearly £65,000, we had hoped the Aslef leadership would engage constructively to move talks forward, rather than staging more unnecessary strikes. We can only apologise for the disruption.”

Students at 150 universities across the country, including Imperial, UCL, King’s College and the LSE, were hit by action by lecturers.

Many London schools battled to continue to provide services for vulnerable children on Wednesday.

At some schools, different classes in the same year group were sent home, leading to confusion for parents. In others, parents were only told yesterday if their child’s school would be open.

Teachers did not have to give advance warning, meaning some headteachers had to take the decision to close without knowing which staff would be on strike. St Mary’s RC Primary school, in Battersea, was among those forced to close — but children in need of food were able to pick up a packed lunch.

Surrey Square primary school in Elephant and Castle was partially open. Co-headteacher Nicola Noble said: “We will review our plans before each strike day. Obviously no teacher takes the decision to strike lightly.”

Secondary schools that are part of the Harris academy chain gave supermarket vouchers to pupils who normally receive free school meals. Steve Chalke, founder of Oasis, said none of its 52 schools would be fully open but staff would keep vulnerable children fed and warm.

Bus drivers working for Abellio in south and west London belonging to the Unite union walked out — affecting about 50 routes.

Members of the armed forces were standing in for striking Border Force guards at Heathrow. The PCS union called out members across all UK ports and airports in its pay battle. Heathrow said it was operating normally.