LNER has revealed why its new Azuma train – which is being launched in York on Thursday - should help prevent passengers enduring more journeys from hell during future heatwaves.

Some passengers passed out, vomited and suffered panic attacks on trains on the East Coast Mainline last Thursday after conditioning failed just as temperatures outside were soaring into the mid-30s.

One train had to be evacuated, with paramedics treating people who had fallen ill in temperatures said to have reached 40 or even 50C onboard.

The problem initially was the failure of aircon on some carriages but then it failed on entire trains after power cables were damaged in the heat and the trains lost their electrical supplies.This also stranded the trains for hours in the countryside.

LNER said services were halted while power was turned off and emergency repairs could be carried out, and a controlled evacuation was carried out on one of its trains at Peterborough to another train.

“We appreciate conditions on the train were very uncomfortable for those on-board,” said a spokesman.

“Our train crew and station teams along were on-hand with medical support for anyone requiring extra assistance. We apologise to all of our customers who have had their journeys disrupted.

But he also said the new Azumas, which start coming into service on the line from York to London and Edinburgh on Thursday, would be better able to deal with such heat for three reasons.

Firstly, the air conditioning in carriages would be more resilient than on the older current trains.

Secondly, if the power supply failed for an Azuma, it would be possible to switch it to diesel and get the air con operating again.

Thirdly, the switch to diesel would also make it much easier for an Azuma stuck behind another train to take a diversion, because the diversionary route would not need to have power cables.