While the country was repulsed by John Haigh's "acid bath" murders, one cheeky chancer spotted an opportunity for gain.

As the killer languished in Horsham prison in March 1949, a letter from an unknown opportunist arrived.

Now, the contents of the note can be revealed after it was bought for £100 by a Sussex museum.

The author, an un-named 25-year-old from London, did not want to know why Haigh, a Crawley businessman believed to have killed up to 12 people, had committed his crimes.

Nor did he want to vent his anger, or even offer support. He simply wanted to borrow the killer's maroon Alvis car.

The letter reads: "By the daily papers I assume you are a business man of great resource and therefore possess a great understanding of people. So although I am a total stranger to you I believe you will not think my letter impertinent or that I am taking a mean advantage of your present position.

"The point is that I have always wanted an Alvis car and have been saving for one for some considerable time but, as I am only 25 years, I'm afraid I've got quite a lot of saving to do yet.

"Therefore, knowing it might be some time yet before you use your car again, I wondered if you might give me permission to use it until you need it again."

Jeremy Knight, a curator at Horsham Museum, which has bought the letter, said: "The audacity of it is amazing. What we want to know now is what became of the car and was the appeal a success?"

The letter was bought by the museum last week, along with other Haigh memorabilia, including a comb he used in prison, a signature and a prison card.

Their owner, Shirley Williams, is the step-daughter of the warder who looked after Haigh when he was moved to Lewes Prison.

When the convict left his cell, Bruce Kent grabbed the memorabilia and, until recently, it lay forgotten in a drawer in Mrs Williams's Amberley home.

The country was gripped by the acid bath murders.

During Haigh's trial at Lewes Assizes, it was revealed Haigh lured his victims to a workshop he used in Leopold Road, Crawley, where he shot them and dissolved their bodies in vats of sulphuric acid.

It is also believed Haigh drank the blood of his victims.

Haigh was hanged on August 6, 1949, for six murders but he is believed to have killed up to 12 people.