And at 27 human years, Mischief is still living up to his name despite "slowing down a little", according to owners Chris and Donna Thorne.The Guinness World Records has confirmed there is no record holder in the UK at the moment but the previous oldest cat was 29.
Mrs Thorne, 33, of St Austell, Cornwall, said: "It's amazing - he just keeps going on and on."
Mr Thorne, 51, got the black cat from a friend in nearby Launceston as a kitten in 1981.
He still has photographs of Mischief at just a few months old being cuddled at Christmas the same year.
Almost three decades later, he is still a vital part of the Thorne family, and is adored the couple's 20-month-old baby Skye.
"She loves him to bits," said Mrs Thorne. "When he eventually goes we'll have to get another one because she'll be devastated."
She said that despite Mischief's advanced years, he still has a spring in his step.
"His name says it all," she said. "He may be 27 but he still manages to jump over the stair gate and he's round your ankles constantly for food.
"He's an indoor cat now, and he's losing big clumps of fur, but he's still going."
She added: "We'd love to know if there are any older cats in Cornwall. He's lost a couple of his nine lives over the years but it doesn't seem to have affected him."
A spokesman from Guinness World Records said a ginger cat called Spike was the last feline to hold the title of UK's oldest cat but since he died in 2001, there had been no further record holder. He encouraged Mr and Mrs Thorne to get in contact with Guinness World Records.
The oldest cat ever is Creme Puff, who was born on August 3, 1967 and lived until August 6, 2005 an amazing 38 years and three days.
Creme Puff lived with her owner, Jake Perry, in Austin, Texas.
