A blue sign with a diagram showing a branch off the road ahead and the following text.
Forward destinations: London; Reading.
Exit destinations: Marlborough; A346; Swindon (E); A419; Oxford; (A420).
Junction number: 15.
The A419 is a fast expressway that will also take you to the Cotswolds, Cheltenham, Gloucester and the M5. But for some reason the signs here don't want you to know that.