Junior doctors have gone on strike for the first time in 40 years in a dispute with the government over a new contract.

Around 100 picket lines have been set up – many of them in and around London.

HOW LONG WILL THE STRIKES LAST?

Junior doctors are set to provide emergency care only for 24 hours, starting from 8am this morning.

This will be followed by a 48-hour stoppage and the provision of emergency care only from 8am on January 26.

On February 10, there will be a full withdrawal of labour from 8am to 5pm.

WHY ARE THE DOCTORS STRIKING?

The British Medical Association's junior doctors' leader, Johann Malawana, said conditions for junior doctors need to change.

In a video posted to the BMA's Twitter site, he said doctors have "even been unable to get leave for their own weddings despite months - and even up to a year - of notification in advance", adding that the situation "cannot continue".

The basis for the current round of negotiations is the government's offer from early November, including an 11 per cent rise in basic pay for junior doctors.

This is offset by plans to cut the number of hours on a weekend for which junior doctors can claim extra pay for unsocial hours.

Currently, 7pm to 7am Monday to Friday and the whole of Saturday and Sunday attract a premium rate of pay.

Under the government's offer, junior doctors would receive time-and-a-half for any hours worked Monday to Sunday between 10pm and 7am, and time-and-a-third for any hours worked between 7pm and 10pm on Saturdays and 7am and 10pm on Sundays.

This is the first strike by junior doctors over pay and conditions since 1975, although they were involved in the 2012 walkout over pensions.

THE NUMBERS

England has more than 50,000 junior doctors - a position covering all doctors up to consultant level.

They represent a third of the medical workforce, and just over 37,000 are members of the British Medical Association (BMA), which called the strike.

Despite last-ditch talks to prevent today's strike, around 4,000 operations and procedures have been cancelled, with thousands more routine appointments also postponed.

NHS England said 1,425 inpatient operations and procedures were being cancelled as a result of the strike, along with 2,535 outpatient ones.

Some 654 cancellations - 192 inpatients and 462 day cases - are in London.

WHAT ADVICE HAS BEEN GIVEN FOR THOSE NEEDING MEDICAL CARE?

Patients have been told hospitals are under pressure and asked to attend A&E only if they have a genuine emergency.

Instead, patients are being asked to make the most of other NHS services, including GPs, walk-in centres, the 111 phone line and pharmacies.

WHAT DO THE POLITICIANS SAY?

Prime Minister David Cameron pleaded with doctors on Monday to call off the action.

He said: "This strike is not necessary, it will be damaging."

Liberal Democrat former deputy prime minister Nick Clegg told the BBC Radio 4 Today programme this morning: "No-one wants a strike and I understand the public concern about the effect of a strike, but equally my experience is that junior doctors, on the whole, are very hard-working men and women who also understand, as Jeremy Hunt has said, that people fall ill at weekends and need to be properly cared for.

"Something has gone wrong here and the government needs to try to settle this as soon as possible."

Jeremy Corbyn said the government was to blame for the strike going ahead and called on ministers to apologise to junior doctors.

In a message on Facebook, the Labour leader said: "Everybody in Britain recognises and is grateful for the hard work and long hours put in by junior doctors.

“Their treatment by this government has been nothing short of appalling, leading to the strike action in our NHS today.

"No NHS worker takes lightly the decision to strike, but the blame must be laid at the door of this government for the way it has treated doctors and now seeks to smear them in the press.

"It is time for this government to apologise to junior doctors and negotiate a fair deal that gets our NHS working again."

Email your photos from the picket lines to harriet.collier@london.newsquest.co.uk