I have been challenging the Government time and again on the costs of Brexit. We are still woefully short on ​information, but I am on the march, with others, so I warn the Government - they had better be prepared.

The Public Accounts Committee, which I chair, and the Treasury Committee, are already pressing the Treasury and other Government departments about what the total cost will be.

As with the emperor’s new clothes, we need to call it out. Wishful thinking is not enough. It is not about ideology or romance, though many of us hold ideological positions. We need clarity on the practical issues.

We need a decision so that business, and indeed the Government, can prepare. We need the customs union. The alternative is chaos, cost, confusion and huge damage to the UK economy.

Let us be clear: there will be additional costs to the financial settlement, which will be only a small portion of the overall costs. That is the cost we will have to pay for the political exit, but there are the on-costs—the lost opportunity costs.

We need to see the full bill of what it will cost to leave and to have it analysed by the National Audit Office. And we need to have that before any meaningful vote in the autumn.