Motorway cantilever sign
A blue overhead sign suspended over the motorway from a post on the left, with a diagonal arrow pointing up and left, and the following text.
A428 (A361) Daventry; [Solid triangle diversion symbol] [Hollow square diversion symbol]; Rail Freight Terminal.
Junction number: 18.
The A361 starts in Kilsby, not far from this junction, and if you were to follow it all the way it would get you to Bideford in North Devon.