Helmand is a hostile place at the best of times. The largest of Afghanistan's 34 provinces, much of it is an arid wasteland.

In summer, temperatures can reach 46C, while in winter it can be well below freezing. Perched 700 metres above sea level, it's a barren place, just a bit smaller than Ireland, that has earned its local name: the Dasht-e-Margo or the desert of death.

But Helmand has long been a prize in Afghanistan. For 30 years during the Cold War, the province was the focus of massive American aid designed to combat the influence of the then USSR in Afghanistan and "make the desert bloom".

At huge cost, two massive dams and hundreds of kilometres of irrigation canals transformed the arid province into one of the most fertile in Afghanistan.

At the centre of the plan was a new provincial capital. Lashkar Gah was built using American designs with broad, tree-lined streets and brick houses with no walls instead of the traditional Afghan "compounds". The locals called it 'Little America'.

But when the Soviet Union invaded Afghanistan in 1979, 'Little America' was one of its casualties. The trees came down and walls went up.

Afghan farmers opium
Afghanistan accounts for 90% of the world's heroin

Enterprising farmers harnessed America's legacy, using the network of irrigation canals to grow poppy and become the centre of the world's opium production. Afghanistan accounts for 90% of the world's heroin - most comes from Helmand.

Throughout the Soviet occupation, the civil war that followed and then under the Taliban, poppy cultivation grew, with Helmand at the centre of production.

And in the 20 years since the US-led invasion, the area of Afghanistan under poppy cultivation has only grown further. Last year, the UN estimates there was a 37% increase in opium poppy cultivation, with more than half of it grown in Helmand.

Camp Bastion
Camp Bastion became home to 30,000 people with its own bus service, fire station and police force

Over a decade, from 2006 to 2016, 'Little America' would become a familiar place to me as Britain moved in to "Helmandshire".

In early 2006, 3,000 British troops were deployed to Helmand. They set up camp in Lashkar Gah, building a giant air base, Camp Bastion, just southwest of the provincial capital.

That summer, the then British Defence Secretary, John Reid, said he would be happy if British troops could leave Helmand "without firing one shot".

In the autumn of 2006, I flew into Helmand with the head of the RAF. I was the Foreign Editor of the BBC - and it would be the first of 13 visits I would make to Afghanistan during the following decade.

British troops training at Camp Bastion

Camp Bastion was just being stood up - the desert runway meant we had to change planes in Kabul and fly into Helmand on an RAF Hercules, which could land on the makeshift airstrip. Air traffic control was in a portacabin.

But as more and more British troops were sent to Afghanistan, Bastion grew and grew, becoming home to 30,000 people - a town the size of Navan with a perimeter stretching 40km, and its own bus service, fire station and police force.

It got a proper runway, capable of handling the giant C17 military transport jet and an air traffic control tower like those you might see at any airport around the world. Just as well - because at one point, Camp Bastion was busier than any UK airport other than London Gatwick or Heathrow.

The British flag was lowered in Lashkar Gah in March 2014. That October, UK troops withdrew from Helmand after an eight-year campaign that cost 454 British lives. Camp Bastion was left to be reclaimed by the desert.

As the union flag was lowered for the final time in Helmand, the most senior British general in Afghanistan said he was optimistic and that "the Taliban have been marginalised".

Less than seven years later, it's the Taliban flag that flies over 'Little America'. It is they who control the desert of death.