There is something faintly fascinating in observing the responses to the reports of the Christmas party held on December 18th.

1. It did not happen.

This is the line pursued by the Downing Street press office, who should know.

2. If it happened, it followed the rules.

This was the Prime Minister’s version in the House of Commons, although how it could have followed the rules has not been explained.

3. If it happened, it is too long ago to investigate.

This, the least plausible version, is the one adopted by Dame Cressida Dick and the Minister of Justice, who must both know that the police are constantly required to investigate incidents which took place in the distant past. Also, it would be elementary to substantiate as the police will already hold records of who was there (if it happened).

4. It may have happened, but there are more important things to worry about.

This is the line now being peddled by MPs.

All of this would be fine, assuming that it did not happen. But it appears increasingly obvious that it did, as more details of it emerge. So, how does the government extricate itself ? I look forward to the answer.