Jack Burnell-Williams, 18, from Bridgend, died on Wednesday after being found unresponsive at the Hyde Park Barracks at just before 4pm.
A Metropolitan Police spokesperson said: “Police were called at 15:48hrs on Wednesday, 28 September to reports of a man found unresponsive at Hyde Park Barracks.
“Officers attended along with the London Ambulance Service. An 18-year-old man was pronounced dead at the scene. His next of kin have been informed.”
According to the MailOnline, Jack guarded the Queen’s coffin as it was carried from Westminster Abbey to Marbel Arch on September 19.
An Army spokesperson said: “It is with sadness that we can confirm the death of Trooper Jack Burnell-Williams on September 28 at Hyde Park Barracks.
“Our thoughts are with the soldier’s family and friends at this difficult time and we ask that their privacy is respected.”
Family and friends are set to gather to honour his life at Bryntirion Football Club in Bridgend on Saturday afternoon.
His death is not being treated as suspicious.