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Thank you Buenchico
The "rickety railway" looks fun - although I feel it is often better watching rather than riding on steam trains.
I hadn't spotted that The Musée Picarvie is actually just up the road from my hotel - so that looks a must-do
I'd pencilled in a boat trip, but the weather may be of the "cracking the flags" variety & being on the water can intensify the heat even more
I've 'done' Amiens before (the son et lumière at the Cathedral was magical), but Abbeville might mérite le détour.