A British adventurer has been refused permission to use the Channel Tunnel to complete his 36,000-mile walk around the world.

Former paratrooper Karl Bushby, 57, set off from Chile in 1998 and has reached Belgium. Under the terms of his challenge, he is unable to use transport.

He expects to reach Calais, France, in September but was told on Tuesday that his formal request to access a service tunnel had been declined, with a Eurotunnel spokesperson citing safety and operational reasons.

Bushby, from Hull, said: "I've only just been told of the decision and it's early days. Clearly, my team will need to have conversations, but if I have to swim across the channel then I am prepared to do that."

A Eurotunnel spokesperson said: "We are aware of Karl Bushby's desire to walk through the Channel Tunnel as part of his journey. We have carefully considered his request and explored a range of possible options.

"In this instance, regretfully we are unable to accommodate Mr Bushby's wishes.

"The Channel Tunnel's Service Tunnel is a dedicated safety and maintenance route. Closing the Service Tunnel for a period of 15 hours, or over two days, would pose a safety risk to passenger services and impact essential maintenance work.

"Access is also tightly controlled and any activity within it requires detailed planning and specialist support."

'Start paddling'

The spokesperson said the safety of its passengers, staff and infrastructure was its highest priority, and they added it "must ensure that all activity within the tunnel meets strict operational criteria".

They added: "We would like to congratulate Karl on his incredible journey to date and wish him well as he makes the rest of his way home."

Bushby said: "I may have to start paddling again."

He has previously swam in order to advance.

In 2006, he crossed the Bering Strait, which involved swimming across gaps in the ice while wearing an immersion suit.

Last year, the BBC first reported Bushby's concerns that he would not be granted permission to access the Eurotunnel.

Back then, Bushby said: "It would be pretty miserable if it was a no. Even the Russians let me through [their country], despite world tensions."