Mr Cameron said it was a moment to reflect on the “sacrifice and dedication that our armed services give on our behalf”.
It is desperately sad news. Another family with such grief and pain and loss.
Of course the 300th death is no more or less tragic than the 299 that came before.
But it is a moment, I think, for the whole country to reflect on the incredible service and sacrifice and dedication that our armed services give on our behalf.
We are paying a high price for keeping our country safe, for making our world a safer place, and we should keep asking why we are there and how long we must be there.
The truth is that we are there because the Afghans are not yet ready to keep their own country safe and to keep terrorists and terrorist training camps out of their country. That’s why we have to be there.
But as soon as they are able to take care and take security for their own country, that is when we can leave.
The UK currently has about 10,000 troops in Afghanistan, of whom 8,000 are based in Helmand.