British troops secretly returned to the scene of some of the Afghan conflict's bloodiest fighting to help government forces battle insurgents.
About 80 British soldiers travelled to Sangin to fight alongside the Afghan National Army (ANA), just months before it assumes full responsibility for the country's security.
The mission was kept secret until its completion earlier this week, and required special permission from Defence Secretary Philip Hammond, according to The Sunday Times.
The Afghan authorities have been fighting the insurgency with little or no help from international forces that have been in the country since 2001's US-led invasion.
All Nato combat missions are planned to end by the end of next year, and the 100,000 foreign troops deployed across the country have already begun to withdraw from the battlefield.
The US provides the bulk of the military presence, with 68,000 troops, with the UK's 9,000 the second most.
Last month President Hamid Karzai announced that the remaining 91 districts under Nato protection were to begin transition to government control, and as withdrawal looms there are tentative parallel efforts to encourage negotiations with the insurgency.
The Ministry of Defence said specialist advisers from the Brigade Advisory Group, made up of the 4th Battalion The Rifles, provided support to the UK-mentored 3/215 Brigade for the eight-day mission, "in line" with their current advisory role.
In a statement, it said: "In support of the Afghan forces who now have the security lead across the country, UK personnel do on occasion operate outside the usual UK area of operations in central Helmand in an advisory capacity.
"These out-of-area operations have been a long-standing element of the UK mission in Afghanistan and are completely in line with our current role of providing training, advice and assistance to the Afghan National Security Forces."
The statement added that Sangin "remains a challenging area" and it is now for the Afghan forces to deal with insurgents.
A number of insurgents were detained and killed during the operation, more than 30 improvised explosive devices were found and destroyed, and two vehicles were seized along with ammunition and weapons.
There were no British casualties, but a number of ANA soldiers were killed, The Sunday Times added.