A vet nervously kept an eye on the tail of a 90kg tiger for signs of it waking as he gave it a medical check up.

Kelabu, a four-year-old Sumatran tiger, was put to sleep with a dart loaded with enough anaesthetic to knock her out for 40 minutes.

Vet John Lewis, 59, said: “We are very careful to keep an eye on the cat throughout.

“We look for signs of it stirring – if it starts blinking, moving its tongue or tail it could wake up.

“We have to check the cat’s health this way as they are good at disguising any problems they may have.

“We give them a full physical examination, paying particular attention to teeth, joints, claws, ears and eyes.

“We feel for tumours and take blood samples.”

Her keeper John Merrington said: “While we work with the cats every day and have watched Kelabu grow up, there are things we cannot check, for obvious reasons.

“That is where these annual vet visits come in.”