The Rules of the Air Regulations 2007

Right-hand traffic rule

16.  (1)  Subject to paragraph (2), an aircraft which is flying within the United Kingdom with the surface in sight and following a road, railway, canal or coastline, or any other line of landmarks, shall keep them on its left.

(2) Paragraph (1) shall not apply to an aircraft flying within controlled airspace in accordance with instructions given by the appropriate air traffic control unit.