Passwords and card details were not accessed, it said.

"This is a painting of unique historic and cultural significance. It would be great if it could be seen and appreciated more widely, whether in India or elsewhere," Caspar Leighton, a great nephew of the artist, told the BBC.According to Bonhams, Clare Leighton "was one of the very few artists admitted to his office and was given the opportunity to sit with on multiple occasions to sketch and paint his likeness".

The works remained in the artist's collection until her death in 1989 in the US, after which it was passed down through her family.She was introduced to Gandhi through her partner and British political journalist, Henry Noel Brailsford, who was a strong supporter of India's independence movement.In November 1931, Leighton showcased her portraits of Gandhi at an exhibition at the Albany Galleries in London.

Though Gandhi did not attend the opening event, several representatives from the Indian delegation of the second Round Table were present.Among them was Sarojini Naidu, also an eminent Indian independence leader, who was one of the key advisors to Gandhi at the meeting.

The exhibition included a charcoal sketch of Gandhi, asleep in his office, along with the oil portrait that is now set to be auctioned.

About the painting of Gandhi, British Journalist Winifred Holtby wrote: "The little man squats bare-headed, in his blanket, one finger raised, as it often is to emphasise a point, his mouth"He went around on foot recording these scenes, like Park Street and Christmas Steps, and they are just fantastic.

"They have a lot of character to them, a lot of personality, as he did himself."One of the lots up for auction is an oil on board, titled on the back in felt tip pen 'Watershed with Arnolfini, City Docks, Bristol'.

Local artist and fellow Royal West of England Academy (RWA) member Linda Alvis, who knew him well, said: "I'd consider him as Bristol's Lowry, but a more blobby edition of it."She described him as a genuinely nice person who would say hello to everyone as he painted, whilst always wearing shorts.