Afghanistan needs £165 million a year from Britain after troops leave

According to the Daily Telegraph,

"Britain will have to provide Afghanistan with £165 million a year after troops leave to ensure the country does not collapse, according to a  report by the Royal United Services Institute."

Why? 
Why should we spend a brass farthing helping a corrupt regime stay in power?

We should withdraw our troops at once and shift a large number of them to the Falklands.We have no interests in Afghanistan, it has been the cause of a huge loss of British lives for more than 200 years and in all that period nothing has been achieved.
It is an American war.   We joined, I assume, in the belief that we had a "Special Relationship" with the United States and should give them support. Obama has recently made it clear that in his view, such a relationship does not exist, and moving our troops to the Falklands would make it clear both to Obama and to Argentina that we are henceforth putting our own interests first, and that includes a group of once uninhabited islands that we settled long before Argentine was even recognised as a state.
At least, based there, our troops wouldn't get killed on a daily basis by roadside bombs.