The Islamist Taliban group is now back in control of most of Afghanistan, almost exactly 20 years after they were ousted from power by a US-led invasion in which Britain played a prominent role.

The conflict that began with Operation Enduring Freedom in 2001 has led to the deaths of 457 British service personnel.

The sterling cost to the taxpayer is harder to quantify. The British government has released figures, but experts say these numbers significantly underestimate the true total cost.

Official figures

In an answer to a recent parliamentary question, junior Armed Forces Minister James Heappey put the cost of Operation Herrick at £22.2bn, with the money coming from the Treasury Special Reserve, a pot of money often used to pay for wars.

This was reported at the time as the final bill for British operations in Afghanistan since 2001, but that’s not accurate, because Operation Herrick only covers part of the 20-year period.

In answers to Freedom of Information requests, the Ministry of Defence (MoD) provides a breakdown of annual Afghan spending, showing that Britain was ploughing nearly £4bn a year into operations at the height of the conflict between 2009 and 2011.

Operation Herrick officially ended in 2015, but the MoD figures show that the new operation which followed it, codenamed Toral, has cost the taxpayer more than £200m since then.

These figures cover the “net additional costs of UK military operations” – spending over and above the normal cost of running the armed services.

But military analysts say these government figures miss out massive additional costs incurred by the state thanks to the decision to go to war against the Taliban.

Frank Ledwidge from the University of Portsmouth published an analysis of the real total spending in his 2013 book Investment in Blood.

He told FactCheck he included “conservative” estimates of many items of additional spending not counted by the MoD.

These range from the C-17 transport aircraft bought to resupply UK forces in Afghanistan, the cost of maintaining a bigger army than we would otherwise have needed during the period, and the statistical value of the lives lost in the conflict.

Mr Ledwidge calculated that Britain had actually spent around £37bn in 2013.

He thinks this will have risen to £38-£39bn now, calling the government’s estimates “bargain-basement, lowest possible figures”.

But even this larger sum does not include the ongoing costs to the NHS of caring for wounded veterans.

Professor Malcolm Chalmers, Deputy Director General at the Royal United Services Institute, agreed that the figure quoted by the government does not represent the real total cost of the war.

He told FactCheck: “It does not include the costs of the Armed Forces Compensation Scheme for veterans, or extra costs incurred by the NHS or charities. I estimate at least an extra £2bn for the first of these.

“Nor does it include the very substantial diversion costs within the MoD – diverting resources from other defence purposes to this mission, especially in the 2006-2014 period. Hard to quantify, but probably the biggest of all.

“Not least, it is expressed in cash terms, not in today’s prices. This would increase the total by some £4bn.”

The verdict

Recent figures put out by the British government put the total cost of major operations in Afghanistan in the low twenty billions.

But independent analysts think the true operational cost could be around double that figure.

And this is without trying to count the additional costs to the health service of caring for wounded veterans over their lifetimes.