One of the bulbs in the shop's celebrated external array of 500,000 Christmas-lights had developed a slight fault and Mr Joynter had hit upon the brilliant idea of running a temporary auxiliary power-cable from the DC traction-rail of the Piccadilly underground line just 10 feet below Harrods' capacious wine- and trout-cellars.
Mr Joynter had begun drilling just after the store opened this morning and, having encountered and circumvented Messrs. Thames Water's Main Western Outflow Sewer and a gas-main, he was soon to be seen by surprised passengers descending through the ceiling of the westbound platform at Knightsbridge station.
Working quickly between trains, Mr Joynter hot-spliced some standard issue 1kv cable to the still-electrified track and, grasping the thick wire between his wizened knees began his ascent back into the bowels of the department-store. It was at that moment that things began to go wrong.
"It all happened so quickly," said Mr James Aspen of Chiswick, a fellow-employee of London Electricity who happened to be waiting on the platform. "Mr Joynter had lit himself a celebratory cigarette and, just as his unmistakable wellingtons were disappearing into the hole, we heard this loud crack followed by the sound of rushing water. Mr Joynter then reappeared through the ceiling followed immediately by a good deal of untreated sewage.
"Then I noticed that a train was on its way into the station and I could see the startled look on the driver's face as he tried vainly to come to a halt. At this point Mr Joynter's generously-proportioned posterior hit one of the running-rails and, simultaneously, the severed piece of cable which he had been climbing up came into contact with the negative return rail in the center of the track.
"There was then a big, blue flash and an enormous bang, followed by an eerie silence which was only broken by the sound of cascading sewage and the hiss of escaping gas. Then the lights went out."
Mr Mohammed al Fayed, commenting from his candle-lit office on Harrods' top floor, said: "We humbly apologise to Her Majesty and the rest of the royal family for the most inopportune interruption of their electricity supply. Also to the intensive care unit at the Chelsea and Westminster Hospital and the staff of the London air-traffic control centre at West Drayton, to whom I shall be sending one of our celebrated Christmas-hampers.
"May I extend my deepest sympathy to Mr Joynter's widow and to his former colleagues at London Electricity, who will be hearing from my solicitors in the morning."