A collection of letters written by one of Britain's most notorious killers during his trial and as he awaited execution are to go up for auction.

Dr Harvey Hawley Crippen was hanged in 1910 after poisoning and dismembering his wife and hiding her remains under the cellar floor.

The US-born physician was arrested as he tried to flee the UK with his mistress Ethel Le Neve, who was disguised as a young boy.

He was captured after the captain of the SS Montrose, the ship he was escaping on, contacted British authorities using new wireless communication.

The third page of a letter written by Dr Harvey Hawley Crippen to Lady Henry Somerset (Henry Aldridge & Son/PA Wire) (Henry Aldridge & Son/PA Wire)

His trial at the Old Bailey lasted five days before he was found guilty by a jury after 27 minutes of deliberations. He was hanged at Pentonville prison, London, the following month.

The letters are expected to sell for between £3,000 and £5,000 when they are sold at Henry Aldridge and Son auctioneers, in Wiltshire, over the weekend.

The letters offer an insight into the mind of the killer as he awaited execution.

In the final letter, dated 26 October 1910, to Lady Henry Somerset, Crippen displays optimism over his appeal and that "all may yet come right".

The fourth and final page of a letter written by Dr Harvey Hawley Crippen to Lady Henry Somerset (Henry Aldridge & Son/PA Wire) (Henry Aldridge & Son/PA Wire)

In the letter he writes: "I shall only be allowed to write you this one letter and to receive the one visit.

"It was most good of you to write me at once after the trial and I had two letters from you and two from Mrs Brock and Mr Brock all at one time, indeed a great solace to me.

"Yes I am going to appeal but I must have Mr Newton's help to fill in the papers.

"I have today a letter from Mr Brock saying Ethel has been taken away with her sister to a safe place and that he is writing to you so possible you may have seen Ethel before you have this.

"I have already told you I hope Ethel may have a little advanced her on my securities by Mr Newton but until I see him.

"I do not know how she will be situated, I have sent word to her by her sister ... she (Ethel) is to see you and decide for herself what to do but I am sure Ethel will trust you and you may guess what a relief to my mind your promise of a home for her has been as I know her sister and brother in law cannot afford to keep her and again, after the happy years with me, it breaks my heart to think of her ever going out in this world again to battle for herself.

"Her health would soon break down, my poor little wifie, I could not bear to think of it.

"I want you please to all get together, I mean you, Ethel, her sister and brother in law, and talk matters over ... let me know as soon as you can what you decide on.

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"I appreciate and entirely understand all you write me and believe me far from finding your letter cold the sympathy they contain and what you tell me about Ethel has been of great comfort to me.

"I am most comfortable in my bodily wants, I eat well and sleep well and be assured I am not all broken down.

"Mr Newton will assist me in making a strong appeal, so hope it is not entirely gone yet. I am allowed to have my glasses and all the books I want to read and everyone tries to be kind to me so I try to rest content for the present.

"I have tried to think of everything knowing this will be my last letter to you, as I am only allowed this one to you, but if there is any point I have omitted, please make a note of it and we can talk of it when you come to see me.

"I want Ethel to see this letter please, when you come to discuss matters, as it may help her in deciding to be with you, now please forgive me such a xxxxx but I have had to write with a quill and I cannot help the scribbling affect.

"Lastly, dear Lady Somerset, I trust to your promise and can only say, My God be always good to you as you deserve, comfort and care for my little wifie and believe that an eternal gratitude is always yours from Yours most sincerely HH Crippen. I am still hopeful and all may yet come right."