What do Fiona Bruce, Conor Burns, Suella Braverman, Howard Flight, Andrea Leadsom, Esther McVey, Priti Patel and Liz Truss have in common?

Answer: all, according to ConservativeHome’s files, were members of David Cameron’s A-list – which legendarily contained only “the pseuds and poseurs of London’s chi-chi set”, in the immortal words of John Hayes.

This casts perspective on the claim that the A-list is responsible for taking a mass of people with no Tory record or beliefs at all and turning them into Conservative MPs – including this week’s three defectors.

The list was an eye-catching idea with which Cameron could be personally associated – and not a very good one.  It was scrapped after the 2010 election.  But it can’t credibly be blamed for the Group of Three.

Sarah Wollaston doesn’t seem to have been on it at all.  Heidi Allen entered the Commons in 2015, long after the A-list’s abolition.  So only one out of the three defectors had anything to do with it.

Maybe Open Primaries are to blame instead?  Except that the Conservative Party only held two proper, full, postal ballot open primaries before the 2010 election.

One of them, to be sure, produced Wollaston.  The other gave us the impeccably orthodox Caroline Dinenage, who has caused neither the leadership nor the membership any trouble whatsover, and is currently a Minister of State at the Department of Health.

Or is the problem selecting MPs who have no sustained history of Party membership?  That’s nearer the mark – fitting Allen and Wollaston like a glove.

However, Soubry’s engagement with the Party stretches back for 40 years or so.  (And please note: she denies ever having joined the SDP, though she is certainly making up for it now.)

And in any event, there are plenty of relatively recent arrivals whose politics is a very long way from being pink.  We present to you, by way of example, Steve Baker, who was fairly new to party politics when selected in 2010.

No, the only rule of defections is that there is no rule: blame the A-list if you like; complain about Open Primaries; look for a lack of long Party experience as a common factor.

But you might just as usefully ask some questions.  Is the defector’s day on the front bench over?  Is his or her career frustrated? Is she a soloist?  Is his constituency markedly pro-Remain? The answers are likely to be a more reliable guide.