It was the fixed stop for the iron gates that was 3" proud of the road.
The Aero has 4" ground clearance and as we had been through the same gate 2yrs ago I thought nothing of it.
The problem was the road had subsided each side so the effective height was >4" hence the damage.

I am about to enter correspondence with Aalborg commune!

PS Does anyone know whether there is a regulation for the minimum ground clearance for new cars?