The soldier was taking part in a reassurance foot patrol alongside the Afghan National Army in the vicinity of Forward Operating Base Keenan, north east of Gereshk in Helmand province, when the incident happened.
Despite the very best efforts of his colleagues around him, he was killed instantly as a result of an explosion; the cause of which is being investigated.
Spokesman for Task Force Helmand, Squadron Leader Wayne Palmer, said:
"The loss of a guardsman, and a colleague, has come as a huge blow to us all. But it is the family, friends and loved ones, as well as the men and women who served alongside him, who feel the greatest pain and we offer them our deepest and heartfelt condolences, thoughts and prayers."
Next of kin have been informed and have asked for a period of grace before further details are released.