This article was written by John Ormerod and was first published in The Evening Press in October 1999.

At about 4.24am on Thursday, 27 October 1949, the many residents on the eastern side of York who were rudely awakened from their slumbers might well have wondered if they had just experienced a nightmare about the Blitz.

In fact they had been awakened by a massive explosion at York Power Station situated on Foss Islands Road, on the site currently occupied by William Birch, Office World and Halfords.

The explosion occurred when a riveted joint on Boiler No 1 gave way. The instantaneous release of the stored steam energy broke the massive boiler into three main parts each weighing up to 25 tons, propelled them through the walls and roof of the boiler house and engine room and deposited them as far as 150 feet away.

Extraordinarily one piece of the super-heater had landed inside the cooling tower which was 120 feet high and some 300 feet distant on the opposite side of the river Foss. Two sections of the boiler wrecked the waste destructor building and the third brought down the overhead cranes. Foss Islands Road was completely blocked with debris and destined to stay closed to traffic for some time for safety reasons.

In 1949, 18 months after the York Corporation Electricity Department was nationalised, the Power Station was being run by the British Electricity Authority.

Normally the station did not run during the night and York was supplied entirely from the National Grid. However on this particular night work was being carried out on one of the two incoming Grid circuits and one generator was running from Boiler No. 1 as a backup in the event of problems on the remaining Grid circuit.

There were nine staff on duty at the time of the explosion: Joseph Percy Wood, charge engineer; Francis Geoffrey Shackleton, switchboard attendant; Timothy Snowden, turbine driver; Eric Smith and Douglas Winn, stokers; Jack Wilkinson and George Stead, fitter and mate; Arthur Henry Horwell, plant attendant; and James Duncan, ash plant attendant.

Just after 4.22am, after discussing an earlier problem with Smith and Winn in front of Boiler No. 1, Shackleton decided that it was time to prepare for his next set of readings and he left to enter the engine room by a door at the south end of the station. However, he had a sudden change of mind, and went the opposite way.

At the same time Smith and Winn decided to brew some tea and proceeded after Shackleton to the north end of the station. It is fortunate that the little get-together broke up at that moment and that the participants went in the directions they did, otherwise none of them would have lived to tell the tale.

Less than two minutes later Shackleton recorded in his own account that he was on a gantry over the engine room when there was a terrific explosion and everything went black. Together with Tim Snowden the turbine driver, he made for the exit as debris rained down. Snowden managed it with nothing worse than cuts and a sprained ankle. Shackleton remembers that he was hit on the head by debris and briefly trapped, but that he quickly freed himself and escaped into the road.

He vividly remembered the tremendous noise and a firework display of sparks from the 3,300 volt oil filled switchgear which had been damaged allowing oil to escape and then set on fire.

York Press:

Having collected his thoughts, he then made his way back into the devastated engine room climbing over the rubble to reach the control room. By now it was about 4.28am and he called the emergency services. He then realised that not all supplies had been lost. The 11,000 volt system was still in operation and feeding most of the city and the suburbs.

What of the other staff who were on duty for that shift? The charge engineer, Percy Wood, in trying to get out, fell down a manhole which had had its cover blown off, and suffered back injuries. George Stead was found by a policeman wandering on Foss Islands Road. He had been having a cup of tea in the mess room and had been blown straight through the window.

Eric Smith and Harry Winn had been propelled along the boiler aisle by the blast. Smith was dazed but Winn had the presence of mind to shut down the remaining boilers. Jack Wilkinson and James Duncan were well away from the explosion and were not physically hurt.

That only left Arthur Horwell to be accounted for. He had been working alone, possibly in the basement. There was the slight hope that he could have wandered off suffering from loss of memory. Unfortunately that was not to be so and his body was found five days later under hundreds of tons of rubble. He was known to be a very conscientious worker and well liked by his colleagues.

Six of the other staff were injured and five received hospital treatment. However all on duty at the time suffered mental trauma to varying degrees as a result of their experience. There was of course no counselling available in those days!

Considering the scale of the damage, electricity supplies in York were not too badly affected. The direct current system was entirely out of action, and a limited number of large businesses fed direct from the 3,300-volt system were also off supply.

Those affected included Rowntrees and Gansolite in Haxby Road; Terry's Clementhorpe factory, Adams Hydraulics and Yorkshire Hygienic Laundry in Peasholme Green; and the Yorkshire Evening Press in Coney Street.

Engineers from the North Eastern Electricity Board, which was responsible for the distribution of electricity within the city, set to work to re-route supplies away from the power station. By lunchtime on the day of the explosion most of the main supplies had been restored.

The Evening Press editorial for that day offered sympathy to those who had suffered and thanked the electricity workers for their efforts. It also appealed to the citizens of York: "Don't switch on if you can do without current".

An official inquiry was set up to determine the cause of the explosion. The examinations revealed that capillary action had caused a concentrated solution of caustic soda to build up in the minute gaps around the rivet holes, which under the particular conditions of pressure and temperature reacted with the steel to cause the cracking. This led to failure of a riveted seam.

It was not then known that caustic soda solution could creep into crevices and concentrate itself by a factor of several hundred times.

The York explosion helped to prove this and revise the way that boiler feed water was treated.

Geoffrey Shackleton summed up his account thus: "The only consolation about the whole episode is that if it had to happen, then it happened at the best time.

"If the explosion had occurred during the day it is likely that many more people would have been killed or injured."

Thanks are due to the family of the late Geoffrey Shackleton for making available his personal account of the tragedy