Zak Brown says he is now 'non-stop cautious' of snakes after suffering an 'elephant leg' from the venomous bite

A father's paddleboarding trip descended into chaos after he was bitten by Britain's only venomous snake, leaving him hospitalised with severe swelling.

Zak Brown, 39, was paddleboarding with a friend at Cavenham Heath National Nature Reserve in Suffolk on May 1 when they stopped for a break.

The business owner from St Ives, Cambridgeshire, accidentally stepped on an adder hidden in the grass as he climbed onto the riverbank.

Moments later, he felt an intense stabbing pain in his left ankle before spotting the snake attached to his heel.

The juvenile adder, measuring around half a metre in length, had injected venom.

"As I climbed off my paddleboard, I walked up the grass verge and within seconds of standing there I just felt this bang on the back of my left ankle," Mr Brown recalled.

"I jumped up because of the pain and saw this snake hanging from my ankle."

Mr Brown said his foot quickly began to swell before he faced a two-hour journey back to his car.

"Within half an hour, my foot started to swell up around my ankle," he explained.

"The pain was spreading up my leg. I thought I might have to phone the air ambulance."

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"I couldn't even stand on my leg - I just fell straight over. My whole foot and calf was swollen like an elephant," Mr Brown said.

By the time he reached Addenbrooke's Hospital in Cambridge, the swelling had spread from his foot to his groin.

Doctors treated him with anti-venom and kept him in hospital overnight before discharging him the following day.

Mr Brown said medics told him he had been fortunate because the snake was still young.

"The doctors said if the snake was a full-grown adult, it could've been a different story and I was lucky in that sense," he said.

"It was a juvenile snake around half a metre. I was lucky it wasn't a full adult adder."

The swelling lasted several days, leaving him unable to wear shoes for almost a week.

"Now I'm non-stop cautious of snakes, constantly looking around the grass checking because I don't want it to happen again," Mr Brown admitted.