At PMQs today, the question was: votes or sunbeds at sixteen?

David Lidington bravely claimed that 16-year-olds were too immature to vote because they can’t use a sunbed, the identical claim that shut them out of the great grown-up debate that was the EU referendum

You spend an eternity waiting for a single solitary reason to watch Prime Minister’s Questions, then three come along at once. One was Emily Thornberry, another David Lidington, standing in for Corbyn and May respectively and doing that rare thing on these occasions, of not giving every outward impression of wanting to be absolutely anywhere else.

But the third stole the show. A single robin redbreast, first spotted in the chamber at around 11am, and still fluttering with intent when the Speaker had no choice but to begin the session at noon.

As new de facto Deputy Prime Minister David Lidington, an affable if armsy fellow (a term in no way related to its close cousin, handsy) got underway, most backbenchers simply gazed excitedly up into the rafters, where the little chap had resettled after a lengthy spell in the press gallery.

For several Conservatives present, you did get the sense that this might have been the first time they had inclined their necks skyward to spot a panicked bird and not then immediately shot it.

Did I say chap? A disgraceful assumption for which I immediately apologise. It may just as well have been a lady redbreast, though round here it’s unlikely.

Thornberry began proceedings by pointing out that next week marks a hundred years since the beginning of women’s suffrage, but yet, “155 Davids” have served as MPs, and she is “the only Emily”.

An extraordinary start of course, but there are other Emilies out there who might feel their contribution to the sisterhood cause has been a bit overlooked, not least that one that got killed by the king’s horse at the derby.

All this was a precursor to a discussion on votes at 16, to which the Shadow Foreign Secretary dedicated almost all of her questions. It was, she said, “an idea whose time has come”.

It is also, conveniently, an idea that would be of electoral benefit to the Labour party. Indeed, at the 2017 election, the crossover age at which a voter became more likely to vote Conservative than Labour was 47.

But Lidington’s response lands him in a particularly difficult bind. He ventured that 16-year-olds do not have the required “maturity” to vote, as compared to their 18-year-old counterparts.

We will not dwell too long on the collected maturity of his own party, which really is about to make everyone in the country poorer for a course of action whose only concrete “upside” thus far has been the “return” of the blue passports that used to be black.

If you’re going to accuse 16- and 17-year-olds of being too immature to vote, it’s best to check whether or not your own party is in the middle of an Instagram- and Snapchat-focused “youth” drive.

MPs have genuinely been sent to secret Instagram training sessions. Indeed, as recently as yesterday, ambulant pork-markets GIF Liz Truss posted a video of herself walking into a think tank to give a speech on the dangers of a planned economy.

Accuse 16-year-olds of immaturity if you like, but just make sure you’re not also frantically lowering yourself to their imagined level.

For around the eighth time in the last couple of years when this question has been raised, Lidington turned to the sunbed defence. That Labour has previously suggested 16-year-olds are too young to use a sunbed, so therefore shouldn’t have a vote. It was for this reason, in fact, they were denied the chance to participate in that great carnival of enlightened debate that was the EU referendum.

There is an impasse to all this, by the way. Just give 16-year-olds and 17-year-olds their own referendum. Which would you rather have: electoral enfranchisement or sunbeds? If they take the responsible decision, well they’ve proved themselves worthy. If they vote sunbed, they’ll be easy to spot at polling booths.

Oh, and what was Liz Truss’s take on all this?

“Brilliant skewering of Thornberry on Labour inconsistency on age of majority,” she tweeted. “Should be able to vote but not use a sunbed! #backofthenet #liddersonfire #pmqs”.

Hashtag back of the net? Liz Truss is 42. Perhaps the maturity question should be judged on a case by case basis.