Paul Curphey was at the iconic tower with his partner Treasaidh when they suddenly spotted someone ‘waving’ at them through their window.
Understandably, given that they were on the 40th floor - the couple were quite surprised by the sight of the bloke, but say they couldn't resist urging him on to complete his journey up the building.
Paul, 52, said: "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.
"It was scary to see, but his happy demeanour was amazingly uplifting.”
It’s since been reported that the climber was a man named Adam Lockwood, who had earlier shared a smiling selfie of himself standing on the edge of the 310m (1,016ft) building while tagging himself at The Shard.
Lockwood is a notorious free climber, having previously climbed the 262ft San Siro Stadium in Milan, done pull ups off the end of a 1,115ft tall beam at a power station in Croatia, and pretended to be a workman to get past security and scale a 1,200ft crane in Dubai.
Metropolitan Police have since arrested three men in relation to the incident.
In a statement, the Met Police said: "Police were called at 05:38hrs on Sunday, 4 September following reports of a climber on The Shard. Officers, London Ambulance Service and London Fire brigade all attended.
"A number of cordons were in place while emergency services responded to the incident. A 21-year old man was arrested on suspicion of trespass.
"Two other men were both arrested on suspicion of causing public nuisance."
An ambulance was also called to the scene but the crew confirmed that there were no injuries sustained by anyone involved.
"We were called at 5.40am today (4 September) to reports of an incident at The Shard, London Bridge Street," London Ambulance Service said in a statement.
"We sent an incident response officer to the scene but there were no casualties."Featured Image Credit: PA/Facebook/Adam Lockwood
Topics: UK News