The British commander in Helmand says talking to grocers and butchers has convinced him that progress is real. But is it sustainable?

Convincing people the military strategy in Afghanistan is making progress is one of the toughest tasks facing British commanders, especially in the face of headline-grabbing attacks by the Taliban, and the rise in 'green on blue' murders of Nato troops by their Afghan colleagues.

Brigadier Doug Chalmers chose not to rely on statistics about violence and the number of bombings to make the argument at a briefing on Tuesday; recently back from his fourth tour of Afghanistan, he chose tomatoes and cattle as his preferred metric.

The outgoing commander in charge of Task Force Helmand, Chalmers has been monitoring perishable foods during the last six months. And by talking to the stall holders in the market, he said he got the unvarnished "crystal truth" about the state of Helmand.

His military peers, he said, often told him what he wanted to hear.

"I ended up talking to butchers and grocers. I picked them because the Afghan capacity to eat meat is unrivalled on the planet, and the need for them to get a good supply is quite prevalent. On earlier tours I saw they were only really selling goat and chicken and on this tour i saw a lot more beef. Now, cattle is expensive, and when you slaughter a cow, with a lack of refrigeration, you need to have the confidence to sell that cow. I saw a lot more cattle being slaughtered, and a lot more cattle in peoples compounds."

It was the same for tomatoes, he said.

"I became fixated by tomatoes... it is quite a soft fruit and easily damaged, and again there is a lack of refrigeration. The market stalls were never without tomatoes. And the ability for them to be moved from the villages to the market towns was a good indication of the freedom of movement that the stall holders have. They were just able to drive in to the markets. From those two elements I got a sense of the micro economics in the market towns and cities."

The argument about progress is really an argument about starting points and end points. If you look at Helmand from the position it was in when British troops first arrived in 2006, then life for most people has improved.

Most people live in the market towns and cities where you can buy the fruit and meat the Brigadier speaks of. There are more schools and more medical clinics than Helmand has ever had before.

But is Helmand what the British, and Nato, had once hoped it could be? That is, a province free of violence, emptied of insurgents, able to sustain itself on tomatoes and cattle, rather than poppy?

Absolutely not. Helmand is still the most violent province in Afghanistan, and one of the districts where the British remain - Nahr-e Saraj - is the most violent within it.

Chalmers points out that most of the attacks have been "displaced away from the population centres...it is now focused in the northern end of the Upper Gureshk Valley."

He also says the British are "no longer the central pillar of the counter-insurgency fight...we are enabling and in the margins."

All of which is demonstrably true. But whether these improvements are sustainable is another matter, and whether they have come at a price that has been worth paying, only history can judge.

In fairness, a proper verdict on the UK's involvement in Afghanistan cannot be passed now, or even at the end of 2014 when Nato has withdrawn all its combat troops.

It will come when it is obvious the 'progress' - whether measured in tomatoes or levels of violence - has been stabilised, or improved upon. And after everything they have been through, would most Afghans bet their livestock on that?