Barefoot man climbs the Shard tower in London

Adam Lockwood made it to the top of the massive tower. Photo / Facebook/Adam Lockwood

A couple staying on the 40th floor of the Shard have spoken about spotting a barefoot climber ascending the London skyscraper on Sunday morning (UK time).

Paul Curphey saw the man as he made his way up to the top of the 72-storey tower and said he was "yelling in celebratory fashion".

"We couldn't help but urge him on to complete his mission," he told the UK's Press Association.

"He was smiling, waving, and having the time of his life.

"(My) partner thought I had pulled all the stops out and managed to get a guy to bring a box of Milk Tray for her birthday," he added.

"It was scary to see, but his happy demeanour was amazingly uplifting."

The climber, Adam Lockwood, later posted a photo of himself at the top of the tower.

Lockwood is well-known for his free climbing antics and has previously climbed thee San Siro football stadium in Milan and a crane in Dubai.

The Shard, opened in 2012, stand at 309.6m high - fractionally smaller than Auckland's 328m Sky Tower.

It is the tallest building in the United Kingdom, and the seventh-tallest building in Europe.

Those high times were short-lived, however, as Lockwood and two men were later arrested by police.

The Metropolitan Police said a 21-year-old man had been arrested on suspicion of trespass.

Two other men were arrested on suspicion of causing public nuisance.

The last person to reach the top of the skyscraper was 20-year-old George King-Thompson in July 2019.

He received a stint in a young offenders institution for his trouble.