Boris Johnson was spotted in a supermarket while on holiday in the luxurious Cayman Islands sporting "messy hair" and wearing neon trainers."

The former British prime minister, 61, was seen pottering around a Fosters store in West Bay, Grand Cayman, last Monday (12/1).

A bystander, who doesn't wish to be named, spotted him entering the shop wearing neon green shoes and his swim shorts at 7pm local time.

He pointed out items for sale and holding his youngest daughter, Poppy, eight months, while his wife, Carrie Johnson, 37, shopped for provisions, the onlooker said.

They said: "He looked hilarious."

"His hair was even messier than usual."

"He was instantly recognisable. I'd know him anywhere no matter how he was dressed."

"It was quite cute watching him show his little girl all the things in the shop."