Michel Barnier, the Frenchman negotiating for the EU over Brexit, has told us that Britain will be faced with an exit bill of £50 billion upon leaving the European Union:

Britain will be presented with a £50 billion “exit bill” by the European Union as soon as Theresa May triggers Article 50, the chief negotiator for Brussels is warning.

Michel Barnier has told colleagues that the UK must keep paying “tens of billions” annually into the EU budget until 2020.

The bill would include the UK’s share of outstanding pensions liabilities, loan guarantees and spending on UK-based projects.

Some of this is not sensibly to be included - loan guarantees are payable when loans fail for example, not before. It's also a terribly interesting accounting - this is what the EU already costs us, without the actual running costs of it on an annual basis. The accruals of amounts already owed that is, without the further payments that would be made if we stayed in. 

Which puts that £350 million a week claim in an interesting light, doesn't it? 

However, the general concept seems sound enough. When you give up a lease on a flat you do indeed pay the last bit of the electricity bill, the gas and so on. We might think that we can manage, perhaps even decide upon, Peter Mandelson's pension ourselves (and that is very definitely included in this sum) but let's not allow personal taste to intrude upon such matters.

However, when you do leave such a lease you also get paid out on any improvements you have made to the capital value of the property. And over our decades of membership a number of improvements have been made. There's a substantial landed estate for example, various parliament buildings dotted around, agencies in many major European cities, embassies in most major world capitals. All of these are owned by the EU and have been paid for from the various payments into it by the national governments.

Britain has also been one of the very few such national governments consistently making net payments into the system too. We thus have an argument that a substantial portion of that capital estate is ours and needs to be returned to us.

And it will really be very interesting indeed to find out whether the tail end of the running costs, which is what is being demanded, is larger than the capital value of the estate we've already paid for. For if it is then that's a statement that the EU is simply a drain on us as we pay for it. Only if that capital value is larger than the running costs can we say that the system is a net wealth builder - which might be useful in portraying the EU as worthwhile but it would then mean that we would be net recipients of funds upon leaving.