I will explain the reason for my panic and the hastily arranged trip to Peterborough. The reason is not what you might expect.
I had few concerns about re-entering the UK with a five year old travelling on a passport five days out of date. The French passport controllers at Calais, if they are not on a lunch break, coffee break, tea break or on strike, will barely acknowledge that we have passports.
The British border force will be somewhat more vigilant, scan all our passports, ask us to open the sliding windows in the rear so they can see the boys, and instantly notice that their computer has flagged up that Ben's passport has expired. In all probability they will politely point this out and issue a recommendation that we renew the passport soon. In a worst case scenario they will drag us off to some back office and give us a grilling before allowing us to re-enter the UK once they are convinced that we are not trafficking Ben.
My risk assessment of the matter considers all the above to be trivial.
However, the damage to my eardrums from Mrs Amarillo when she finds out that I allowed Ben to travel on an expired passport is a risk I am unable to mitigate by any legal means without an unscheduled visit to Peterborough on Monday.
On a happier note, the train journey to Peterborough from King's Cross is just 45 minutes and costs £14.50; the Cali would take 1h45 for the same journey and be a roughly similar cost in fuel. And this is the car park opposite the passport office:
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