Unpublished letters written by the Kray twins are expected to fetch ST£10,000 when they go under the hammer next week.
The 80 letters were written by gangsters Ronnie and Reggie between 1985 and 1993 in a childlike, barely legible scrawl and provide an insight into the mental state of the twins in their later years.
They were penned to journalist Robin McGibbon who entered the gangland family's inner sanctum after helping Charlie Kray, the twins' brother, to write his autobiography, Me and My Brothers, in 1975.
The letters include the revelation that Reggie once considered getting "engaged" so that the story could be sold to newspapers.
He wrote to Mr McGibbon asking if newspapers would pay a lot for the story - he said he wanted "big money" and asked who the lucky girl should be.
Reggie suggested several candidates, including a model who he claimed had had an affair with a marquis, a page three girl and a soap actress.
In one letter he said "tell me by return of post who is better" and added "I can get a young model if necessary".
He added: "Let's do the engagement in style and go for top money."
Reggie's letters, written on his own personally headed notepaper, also discussed trying to get a campaign together for his release.
He wrote about organising a charity night in an East End wine bar to raise money for underprivileged children and about arranging a parachute jump for a friend.
He also raved about a cell-mate who he said would be "big news" in the pop world and about arranging for him to sing on television.
Reggie denied being homosexual, writing: "I'm not gay. My heart does not beat faster when I see a male - does yours?" and at one point quotes a Sicilian bandit, saying: "I know my enemies but God protect me from my friends."
In other letters he says he is taking up yoga, that he got 300 Christmas cards and is looking forward to a move to Maidstone prison and taking up swimming.
Ronnie's letters include one in which he angrily denounces a book about him by his wife Kate as "diabolical" and says if she does not stop publication he will divorce her.
Another letter, the third to arrive in a single day, reminded the journalist to bring some Players cigarettes when he visited him in prison and some money so Ronnie could buy a drink.
Ronnie wrote in particularly shaky handwriting from Heatherwood Hospital to say that he had angina.
He later sent a letter asking for confirmation that money from a newspaper article had been donated to the hospital and to the taxi drivers' association.
A series of 28 letters included in the sale were written in 1993 and chart the gangster's mental breakdown.
The letters will go under the hammer at Dominic Winter auction house in Swindon on April 11tj.
Other memorabilia being auctioned include letters from the twins' brother, Charlie, written from Belmarsh prison before and during his trial for drugs offences.
There are also photographs of various Kray family members with stars such as Diana Dors and Barbara Windsor.
One photograph shows the future millionaire novelist Ken Follet as a young man with Charlie Kray and Mr McGibbon.
Mr McGibbon, 60, who was running a publishing company which published Charlie Kray's book, said: "Ken was working for me as an editor. Charlie was very impressed by the millions Ken made out of thriller writing - he reminded me later of the time he had to pay for Ken's lunch."
Mr McGibbon said the letters demonstrated a huge gulf between the twins and Charlie Kray.
He said: "Throughout their turbulent lives Ronnie and Reggie Kray were suspicious of newspaper people but as Charlie's ghostwriter and pal I came highly recommended and struck up a strong friendship with them that lasted until their deaths.
"For 10 years I was in a privileged position, cleared to visit Reggie in top-security prisons in various parts of the country and Ronnie in a hospital for the criminally insane.
"As a valued and trusted friend I witnessed the fascinating, contrasting personalities of Britain's most infamous gangsters at close quarters.
"I suffered the irritating mood swings and egomania of the more aggressive Reggie, who would stride purposefully to our meeting place in casual prison gear, interested only in talking about publicity or making money."
PA