Three British soldiers shot dead by a man wearing an Afghan police uniform have been named by the Ministry of Defence.
Guardsman Craig Andrew Roderick and Guardsman Apete Saunikalou Ratumaiyale Tuisovurua of the 1st Battalion the Welsh Guards and Warrant Officer Leonard Perran Thomas of the Royal Corps of Signals died on Sunday.
The men, members of an Afghan Police Advisory Team, had been helping organise a shura - or meeting of elders - at Checkpoint Kamparack Pul in Nahr-e-Saraj, Helmand Province, when they were shot and fatally wounded.
They received first aid at the scene but died of their injuries.
A man believed to be responsible for the shooting is in custody, the MoD said.
Warrant Officer Class Two
Leonard Thomas, Guardsman Craig Roderick and Guardsman Apete Tuisovurua
Defence Secretary Philip Hammond said: "I am saddened to hear of this cowardly act which has taken the lives of three very brave British soldiers.
"My thoughts are with the families of Warrant Officer Class 2 Leonard Thomas, Guardsman Craig Roderick and Guardsman Apete Tuisovurua whose lives were cut short in such tragic circumstances.
They gave their lives protecting Britain's national security; their efforts will not be in vain and we will always remember them."
Warrant Officer Thomas leaves behind his mother Sylvia, long-term partner Rachel, and younger brother Tristan, 43.
WO2 Thomas, 44, was on his final tour in Afghanistan, having served since 1990 in units including the Coldstream and Welsh Guards before joining the RCS.
The family of WO2 Thomas, known as "Pez" described him as "a military man through and through".
"He thrived in extreme environments, both in the military and in his spare time," they said in a statement.
"He was a keen climber and mountaineer and will be sorely missed by everyone who had the privilege to have met him."
Colonel Alan Richmond OBE, commander of the military stabilisation support group, with which WO2 Thomas was serving, said he was "a soldier of great experience, wisdom and dedication".
"For our small tight-knit team in Helmand the grief will be most acute but the loss will undoubtedly strengthen our resolve to get back out and continue his selfless work."
Cardiff-born Guardsman Roderick, 22, was a trainee bricklayer before joining the Welsh Guards in September 2009, based in Aldershot. He leaves behind his parents Mike and Sadie, two sisters Katie and Lucinda Emily, step-brother Jay, grandmother Margaret, and girlfriend Zoe.
Both Guardsman Roderick and Guardsman Tuisovurua were working in a police advisory team mentoring Afghan police.
A passionate Cardiff City fan who had joined the army so he could serve in Afghanistan, Guardsman Roderick was described as having had boundless enthusiasm and a bright future in the service.
"Words cannot describe how the loss of our precious Craig has affected us all," his family said in a statement.
"The vast void left by this tragedy will never be filled.
"Everyone who knew him will miss his big smile and his sense of humour.
"He was the best son, brother or friend you could have wished for, we were privileged to have known him. He will always be missed and never forgotten."
Lieutenant Colonel Dino Bossi, commanding officer of 1st Battalion Welsh Guards, paid tribute to both men.
"Guardsman Craig Roderick died doing the job that he loved - he had joined the Army expressly to go to Afghanistan and was in his element out here thriving on the austere conditions, the hard physical work and the mental challenge of soldiering," he said.
"He was an integral and much loved member of a close-knit team."
Fijian Guardsman Tuisovurua, 28, had been a soldier for little more than a year, having finished his training and joined the regiment in June 2011, based in Hounslow.
He leaves behind his mother, father, four brothers and three sisters, was described as being popular because of his "wonderful smile and relaxed attitude".
Described as 'one of nature's true gentlemen', Apete Tuisovurua had been a soldier for little more than a year
Lieutenant Colonel Dino Bossi added: "Guardsman Apete Tuisovurua was a gentle and decent man who was defined by his love of sport, his uplifting company and his willingness to go out of his way to help anyone.
"One of nature's true gentlemen, he had a deeply moral outlook on life and enduring principles by which he lived. He was extremely fit and robust but without show or arrogance. Everybody liked him - one could not fail to - and his infectious smile broke down barriers wherever he went."
The attack on the soldiers was the latest in a growing number of so-called "green on blue" attacks in which members of the Afghan security or police forces have opened fire on international allies.
Four other British soldiers have died in similar circumstances so far this year.
The Ministry of Defence said there had been 16 "green on blue" UK fatalities since 2008, including the seven killed this year. In 2011, there was only one such death.
Prime minister David Cameron has condemned the killings and said the government would do everything in its power to see that the gunman was brought to justice.