Paul McCartney talks to Des Lynam on BBC Radio 2

Speaking to Des Lynam on BBC Radio 2, the former Beatle tells of the dilemma he faced when he realised the drugs taken by Linda to treat her breast cancer may have been tested on animals.

Sir Paul is a strict vegetarian and campaigner for animal rights, as was Linda who died in April, aged 56.

Linda: died of breast cancer

He said: "I'm finding out now that there is quite a lot of animal experimentation. Some of it, I suppose, absolutely necessary when you come down to the final tests before people.

"I suppose a limited thing is unavoidable, but it is very difficult for me to think like that because I favour the rights of the animals."

Talking about the medication used to treat Linda's breast cancer, he said: "If a drug has got to be used on humans then legally it has to be finally tested on an animal ... This was difficult for Linda when she was undergoing her treatment."

Sir Paul welcomed Linda being on stage with him

Sir Paul revealed that Linda had been kept in the dark about how the drugs she took may have been tested on animals.

He said: "During the treatment, a nice answer is a nice answer and if they (the doctors) say, `It's OK to have this because we didn't test it on animals', you are going to believe them."

Later, in a separate statement, Sir Paul stressed his opposition to animal testing, saying: "I am totally against experiments on animals. I don't know of a case where it is necessary and I haven't been persuaded of any case."

Sir Paul: May perform live again, possibly next year.

During the Radio 2 interview Sir Paul comes close to tears when he talks about how hard life is without Linda.

"We fancied each other something rotten. That's all it was. To me she was always still my girlfriend," he said.

"Our kids used to laugh at us ... we'd be standing in the middle of the kitchen kissing and stuff and they'd say `Look at the state of you two!' and I would say `It's allowed isn't it? We're married'.