Simon Coles (21), of Harrington Street, Bourne, tore the ring finger from this right hand when he fell from a fence and had to be airlifted to Queen's Medical Centre in Nottingham.

He was in hospital for a week following the accident at Toft Tunnel, near Bourne.

Simon said: "Halfway through the week it was not looking good. They told us they may have to put leeches on it and another day said they might have to amputate."

The accident happened when Simon had gone to meet his brother Sheldon (18) and friends at the entrance of the disused railway tunnel.

He was climbing a fence when he slipped and became stuck. He sliced off his finger in his struggle to get free.

Simon said: "They had climbed in. I followed and my jeans got caught on the fence and I was hanging by my leg."

"My brother climbed back over the fence to get my finger.

"The 999 service people said to wrap it in tissue and keep it cold. I started to feel faint as I lost blood."

Friend Katy Compton raced home and grabbed a bag of frozen peas and water to preserve the severed finger.

Simon's mum, Alison Noll, said: "It could have been a lot worse. I had to walk out the room when I saw the injury. They took a vein out of his arm to put into his finger."

Simon, who works for Carlsberg and Tesco in Bourne, said it could be many months before he is able to return to work.

He added: "It could be two years before I get all my proper feeling back."

The land is owned by South Kesteven District Council and Simon said: "I should not have been there but the fence should have been higher. Loads of youngsters go there and I only went to get my brother."

His message to anyone else considering visiting the tunnel is "don't".

He said: "I know that climbing the fence in the first place was a stupid thing to do. I wouldn't make the same mistake again."

Toft Tunnel is part of a nature reserve owned by the district council and leased to the Bourne area group of Lincolnshire Wildlife Trust.

SKDC facilities service manager Paul Stokes said: "Common sense would tell you that gates are there for a reason, in this case to stop people getting into the tunnel.

"The tunnel is home to a bat sanctuary and anyone climbing the gates could harm themselves as well as disturb the bats."