I don't know where you flew from, but I understand that Le Touquet is a customs airport.
See
Arrêté du 20 avril 1998 portant ouverture des aérodromes au trafic aérien international | Legifrance (I don't know how current these lists are).
The number of customs airports is reducing though, see previous thread:
http://www.pprune.org/private-flying...s-customs.html