Did UK intervention in Afghanistan have any value?
As the union jack came down at Camp Bastion in Helmand Province on the UK's 13-year involvement in Afghanistan, there was an unusual amount of introspection in Britain itself.
Was there any real cause for pride? Or had the death of 453 British service personnel been in vain? Had there, indeed, been any value whatever in the British intervention?
The great majority of the ordinary Afghans I have spoken to about this over the years have no doubt about it: the British had helped to shore up this country and make it more stable and prosperous.
'Now,' said a man I came across in the north of Kabul, 'the future is very good, with elections and everything. Before there was nothing like this place here, this road.'
He pointed to the new buildings which had sprung up all round us, and to the well-surfaced road which hadn't even existed before.
These things are the product of investment, of know-how, of confidence in the future: all things that the British and Americans have brought to Afghanistan.
It's hard to find anyone here in Kabul who really thinks the Taliban will return to power in Afghanistan now the foreign troops are on their way out.
Afghanistan, the 16th-poorest country on Earth and the third most corrupt, has plenty of problems. But stability has brought education to millions of children in schools and colleges all over the country.
Young girls are becoming as well educated as boys: a lasting change in the social life of Afghanistan, and something which the Taliban have been entirely unable to stop.
It's true that the Taliban have not been defeated, and that was obviously the main purpose of the UK and US military presence here.
Yet they have not been victorious either, and they have not been able to capture and hold any important town or city.
Nowadays, there are other extreme Islamic movements which we can compare the Taliban with, and it's clear that Afghanistan is quite lucky compared with Iraq, Syria, Nigeria, and other countries threatened by Islamic State or its imitators.
The Taliban is a loose confederation of groups, some of whom are willing to consider negotiating with the government. And their methods are usually much less savage than, say Islamic State or Boko Haram.
The Afghanistan which UK troops are leaving behind isn't altogether safe from insurgency or instability; but compared with the condition it was in back in 2001, it is a great deal more stable.
If it gets better government than the corruption and warlordism of the last few years, it could even turn into a success story one day. And part of the credit for that will belong to the British involvement here.