The nearby Crystal Palace and its transmitter burned down three days after Mr Davis bought the Marconi type–702 set on November 26. The area could not receive pictures again until 1946.

The 75-year-old set comes with a 12-inch screen and is contained in a walnut and mahogany case with the picture being reflected onto a mirror that opens from the top.

There are more 18th century Stradivarius violins in existence that pre-war TVs and this set has only had two owners.

Television pioneer John Logie Baird and the Marconi company were responsible for the set which was created using Britain's secret radar research.

Only 30 per cent of the components in this set have been replaced – all with identical parts – and it works perfectly.

It has a pre-sale estimate of 5,000 pounds, but experts at Bonhams, which is selling it, expect it to sell for much more.

For 5,000 pounds today you could buy a top-of-the-range set with high definition, 3D, surround sound and more channels than you could ever watch.

The set cost Mr Davis 99 pounds. 15 shillings. 0d – over half the annual average wage of the day and equivalent to almost 4,000 pounds today.

Its number is H1007, and it is thought the numbers began at 1,000 meaning this is 007, the James Bond of TVs.

Bonhams specialist Laurence Fisher said: "This is being sold by the late owner's family and is the oldest working TV set in Britain.

"These sets were really a side effect of our secret radar research and they are very similar inside to the radar.

"Logie Baird and Marconi had separate companies but used the same people to make the sets, but Marconi became the most popular maker.

"Baird made the first mechanical television in 1926 and this was the first electronic version.

"I've handled 38 pre-war tells and this is the finest and even comes with the original invoice.

"It cost a huge amount and the owner must have had wealth and means.

"Its case is made from walnut and mahogany to give a two-tone effect and doesn't have wheels and is quite a big lump.

"The picture is reflected onto its lid and at the time it was bought there was only one hour of television a day. And only one channel.

"Unfortunately for the original owner he would have been able to only watch three hours of programmes on it.

"This was because three days after he bought it the Crystal Palace burned down and that was where the transmitter was.

"And his area did not receive pictures again until after the war. But at least people who visited him would know he had one, even if he couldn't use it.

"Programmes at the time would have all be live and there were plays which were grand productions like you would have at the theatre.

"It was the first time people could see the faces of those whose voices they knew so well from the radio.

"It is a very rare thing and there are collectors who would love to have it."

Bonhams Mechanical Music and Scientific Instruments sale is being held at Knightsbridge, London, on April 19.