Novelist Jane Gardam has described penning her memoirs as “the most difficult thing I’ve ever done”.

The writer, best known for her trilogy of novels about an ex-colonial QC nicknamed Old Filth, said it is far easier to write fiction.

She told BBC Radio 4’s Desert Island Discs: “I don’t know what they are. I don’t like the idea of writing my memoirs, it’s a very final thing to do.

“It’s horrific, it’s like being psychoanalysed. You could go on forever with it, it’s probably much better to write fiction.

“You’re always trying to tell the truth in fiction but this is really important that you get it right. It’s the most difficult thing I’ve ever done.”

Investitures at Buckingham Palace
Jane Gardam being made an OBE by the Prince of Wales (Johhny Green/PA)

Gardam, who is approaching her 90th birthday, says she loathes ageing and finds it terrifying.

She told host Kirsty Young: “I don’t think that I like being old at all, I really do not.

“I’m very frightened but goodness, what luck to be 90.

“It’s a physical fear of the next thing that’s going to go wrong but that is the way it was when I was a child, everyone talked about illness all the time, they all lived to a great age, so I have to be as brave as they were I suppose.”

Gardam, who has won two Whitbread prizes, the Katherine Mansfield Award and has been shortlisted for the Booker and the Orange Prize for Fiction, said she still does not know why she writes but said the urge is a physical feeling.

Last Friends by Jane Gardam (Little Brown/PA)

Her certainty that that is what she wanted to do was cemented after following the critic LAG Strong on to a train and striking up a conversation before sending him a short story.

He wrote back to her that he was certain that she was indeed a writer.

Gardam told Young it was writing that helped her process the trauma of falling backwards into the fire at home when she was just six years old.

She said: “I hadn’t realised the fire was so important until I began to write it all down, it almost meant that I couldn’t write anything and do much with my hands for a while.”

Gardam revealed she did not write at all when she was taking care of her three children but resumed the same day her youngest child started school.

She said: “I came back and locked the door and started writing the first book. It was a wonderful release. I just scribbled.”

Desert Island Discs is on BBC Radio 4 on October 15 at 11.15am.