"SINS OF COMMISSION"
I've always said that even the background characters have full lives in Toobworld, and that it might even be possible to use them to connect different TV shows together.
A more "celebrated" example would be the flasher "Buck Naked" who first appeared on 'Hill Street Blues' and then later in an episode of 'NYPD Blue'.
So let's take a look at this guy who's sitting between/behind Cully Barnaby and her mother Joyce:
He's not the traditional "Identical Cousin", but I think there's more than a passing resemblance to Sir Bernard Cribbins to suggest that he's kin to Wilf Mott, one of the Doctor's more beloved Companions since the series was rebooted.
He might even be a younger brother! And why would Wilf have had reason to ever mention having a brother during those 'Doctor Who' adventures in which we saw him?
If I had to spin a backstory for this particular theory of relateeveety, I'd say he was Wilfred Mott's younger brother, Alfred Mott. Like his older brother, he'd be known by the shortened name of Alf Mott.
During World War II, perhaps the Mott boys were relocated from London to the Midsomer area. And perhaps Alf Mott liked it so much that when he was old enough to do so, he relocated there to the village of Midsomer-St. Michael's.
And now we see him enjoying the 12th annual award ceremony for the Maplin Literary Prize....