If Kenneth Graham had ever written a French version of Wind in the Willows, you can be sure it would have including the jailing of Mr. Toad not just for reckless driving but for refusing to pay tolls on the privatised motorways that continue to proliferate across France.

The French courts sit in judgment this month on a real-life toad, whose habitat has brought construction work on one new such motorway to a grinding halt. The rare species in question is the yellow-bellied toad (Bombina variegata), so called because when provoked or attacked the toad flips on to its back to reveal the full extent of its warning colours. The toad secretes a milky toxin from the hundreds of tiny pores located throughout its body and predators who try to eat it get a nasty surprise.

So, too, did the construction team on Autoroute 89, connecting Bordeaux, Clermont-Ferrand and Lyon, a means of crossing the centre of France without passing close to Paris. Their efforts have been frustrated by the discovery of an unknown number of the yellow-bellied animal, each of which is not much bigger than a ballpoint pen. Just one section of about 50 kilometres near Lyon remains to be completed, between Balbigny in the Loire and La Tour-de-Salvagny in the Rhône, and so far the ecologists have succeeded in using the presence of this rare toad as a way of switching off the mechanical diggers. Soon, however, we will know whether the motorway has to be diverted, or whether sadly it will prove to be a case of toad in the hole.