(CNN) -- Prince William's former Sandhurst academy platoon leader was killed in an explosion in southern Afghanistan, making him the highest-ranking British officer to die since operations started there nearly six years ago.
A roadside bomb struck Maj. Alexis Roberts' vehicle west of Kandahar on Thursday as he was leading a convoy back to a base, the British Defense Ministry said Friday.
Roberts, 32, was serving with the 1st Battalion, The Royal Gurkha Rifles, a well-regarded unit in the British army. His death -- which brings the number of British troop deaths in the Afghan war to 82 -- prompted many tributes.
Prince William "was deeply saddened to learn of the death in action of Lex Roberts, who he remembers with great respect as his platoon commander at Sandhurst and as a good friend," the prince's spokesman told CNN.
"At this time, his thoughts and prayers are with Lex's wife, Susie, their two young daughters, Alice and Freya, and with all his family and friends."
Susie Roberts said she had recently received a letter from her husband, who said he was pleased with his work and proud to be part of the Gurkhas.
"Lex was my best friend, the most wonderful husband and deeply loving father to Alice and Freya," she said in a statement released by the Ministry of Defense.
Defense Secretary Des Browne said he was "greatly saddened by the news" and noted that Roberts was "held in high regard by his superiors, peers and those who worked for him," in a statement posted by the ministry.
Lt. Col. Jonny Bourne, commanding officer, 1st Battalion, the Royal Gurkha Rifles, said, "Lex started his service with the Gurkhas in Brunei. From the very beginning his compassion and concern for his soldiers shone through."
Calling him a "true Gurkha," Bourne praised Roberts for his service as an "inspiring" instructor at the Royal Military Academy, Sandhurst.
"It is not always easy to explain the close bonds that develop between soldiers, particularly on operations, but it is a form of love, and a Gurkha community is especially close-knit. Lex was loved by us all," Bourne said in remarks provided by the Defense Ministry. E-mail to a friend
CNN's Jonathan Wald contributed to this report.