YouTuber Adam Lockwood scaled the 310-metre The Shard building in central London barefoot on Sunday.
Mr Lockwood, 21, posted pictures and videos of himself online climbing the building, with one post appearing to show him at the top of the tower.
The Metropolitan Police later confirmed that a man had been arrested on suspicion of trespassing and two other men on suspicion of causing public nuisance, as the London Ambulance Service and London Fire Brigade attended the scene.
A couple staying on the 40th floor of The Shard were in bed when a man waved and climbed past their window at 6am.
Paul Curphey said it was “amazingly uplifting” to see the young man on Sunday.
Mr Curphey, 52, and his partner Treasaidh, were visiting the capital for a birthday trip.
“The climber was yelling in celebratory fashion,” the retail businessman from the Isle of Man told the PA news agency.
In pictures: London’s Shangri-La at The Shard - in pictures
“He appeared, waving at the window, 40 floors up, already in the deep end so to speak. We couldn’t help but urge him on to complete his mission.
“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.”
Mr Curphey said the climber had a “happy demeanour”.
“It was scary to see but his happy demeanour was amazingly uplifting.”