Hospital doctors in England on Wednesday begin their longest consecutive strike in the seven-decade history of Britain's National Health Service (NHS).

Junior doctors -- those below consultant level -- will walk out for six days in a major escalation of their long-running pay dispute with the UK government. 

The industrial action comes at one of the busiest times of the year for the state-funded NHS, when it faces increased pressure from winter respiratory illnesses. 

It also quickly follows a three-day strike held by doctors just before Christmas.