Thank you so much for all your replies - unfortunately didn’t see them at the time as al the alerts went to spam mail...
Update - if you’re interested - is that we re-started the engine having spent an hour mulling over all the scenarios (pretty much all those that you have mentioned). It started and made a strange sound, consistent with expelling a foreign object. Although we couldn’t find it - funnily enough - she ran beautifully and we managed to finish the trip. Silver lining is that my 15 year old son seriously impressed his Dad with his engine knowledge, all recently learnt at Air Cadets, and together they were able to rationalise the situation! Thank you all again. Much appreciated. No cognac on board but there were substitutes ?