Seems this has been leaked and as it is doing the rounds on the internet I thought it only fair that D.com readers should see it as well.
From Number 10 Downing Street. London SW
Dear Santa
As you know, we will no longer believe in you from 29th March 2019.
However, we would like to maintain the closest possible relationship with you even after we have stopped believing. We therefore fully expect to get the same presents as before (you need us more than we need you), but we will no longer have to abide by your rules of being good and stuff.
We will attach a full list of the presents that we want as soon as we can agree amongst ourselves (to tell the truth, we’ve only just started talking about that).
Please also bear in mind that you’ll no longer be able to deliver your presents like before, flying in with the sleigh, as we are taking control of our own borders. Although we do expect you to deliver presents. I’m sure we can come up with some technological solutions to solve this further down the line.
We’re determined to make a success of not believing in Santa!
Whilst still getting you to deliver all our presents.
Yours etc etc
Theresa May and Cabinet
(but now minus Damien Green who’s been a naughty boy)

Please