The flag of Brig Radford's 19 Light Brigade was lowered at the ceremony
A new brigade and commander have taken over UK military operations in Afghanistan, after the bloodiest tour since the mission began in 2001.
The 19 Light Brigade is returning home, having lost 70 men during six months of fighting the Taliban.
They have been replaced by 11 Light Brigade, which has been formed specifically for Helmand.
The new brigade is smaller than the one it replaces, meaning some troops have had to extend their tour in Helmand.
The new brigade includes units from across the UK, and will be made up of the Household Cavalry, 1st Battalion Grenadier Guards, 1st Battalion the Royal Welsh, 2nd Battalion The Yorkshire Regiment, 3rd Battalion The Rifles and 1 Royal Horse Artillery.
It will also include a specialist taskforce to help guard against improvised explosive devices.
British forces spokesman Lt Col David Wakefield told the BBC "real progress" had been made against the Taliban and in redevelopment efforts, but acknowledged there was still "hard work" to be done in some parts of Helmand province.
The flag of the new 11 Light Brigade was raised at the ceremony
Speaking from Lashkar Gah he said: "We will be really focusing on training and working with the Afghan national police and Afghan national army, the people who ultimately be delivering security by Afghans, for Afghans here.
"But there's also all the work on economic reconstruction and redevelopment because those things are important too. We've got to make it so the Afghans want us more than the Taliban so they can go on to deliver their own security and own environment."
The new commander of Task Force Helmand, Brigadier James Cowan, took over from Brigadier Tim Radford in a simple ceremony at the British headquarters in Lashkar Gah just before 0800 BST.
Several of Brigadier Radford's soldiers died during Operation Panther's Claw ahead of the Afghan elections in August.
Two soldiers from the new brigade have already been killed during the past week.
The UK civilian head of the mission in Helmand - diplomat Hugh Powell, who is in charge of the provincial reconstruction team - also handed over to his successor.
BBC defence correspondent Caroline Wyatt says that Brigadier Cowan led his old regiment, the Black Watch, in one of the most dangerous areas of Iraq four years ago, and his forces here will try to move the emphasis away from fighting, towards more reconstruction and winning the support of Afghan civilians.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.