He ventured into the mall armed with a pistol as al-Shabaab militants shot at people indiscriminately on the afternoon of September 21, 2013.
He is said to have rescued more than 12 people and later frisked those he had helped out so that no terrorist could escape.
Mr Troulan was not at the mall at the start of the bloodbath that claimed 67 lives.
He was called by a friend whose wife and daughter were in the besieged mall. The friend wanted his help in locating the two.
“On arrival at the mall, Mr Troulan contacted the family by telephone and entered the mall.
He was armed with only a pistol while the area was dominated by terrorists armed with grenades and machine guns.
Nevertheless, Mr Troulan managed to bring the two women to safety,” says a statement from the office of Queen Elizabeth II in the June 16 issue of the London Gazette.
“Over the course of several hours, he went into the building at least a dozen times and on each occasion managed to bring many innocent civilians to safety.
He was fired on twice by the terrorists but managed to force them back,” the statement adds.
The George Cross award that Mr Troulan received is one of the honours conferred on various people by the Queen on her official birthday.
A Kenyan-Briton Mr Colin Church was also honoured during the Queen’s Birthday. He has been an environmental conservation crusader for two decades.
Mr Church, the chairman of the Kenya Wildlife Service between 2003 and 2004, is best known for his work as the chairman of the Rhino Ark.
Rhino Ark was founded in 1988 that focuses on conserving Kenya’s mountain ecosystems — the Aberdares, Mt Kenya, the Mau Forest complex and Mt Elgon.
He quit his job as a public relations consultant to take over the chairmanship of the Rhino Ark in 2000 when its founder Ken Kuhle moved abroad.
By the time Mr Church left the organisation, he had achieved a number of feats that include coordinating the construction of the Mt Kenya fence, the Eburru Forest fence and starting the Rhino Charge.
The Rhino Charge is a competition where 65 entrants compete for 10 hours on a tasking terrain. Competitors pledge a considerable sum of money to enter and the event currently raises $1.5 million (Sh155 million) annually.
“He campaigned for a holistic approach to species conservation by promoting and financing policies that simultaneously confronted threats to the mountain ecosystem,” says a press statement on Mr Church’s win.
Another Kenya-based Briton, Mr Graham Shaw, also received the Most Excellent Order of the British Empire (MBE) award for promoting British business in Kenya.
Mr Shaw is the chairman of the British Chamber of Commerce in Kenya.