Originally it started on the A40 (now A4020) in the centre of Hillingdon. However, this section is today part of the A437 and the B466 now starts over a mile further north on the current route of the A40 on the edge of Ickenham.
The B466 leaves the A40/A437 GSJ behind and heads north along Long Lane. It starts as dual-carriageway but quickly narrows to S2. We meet the B467 by the church and cross the Chiltern Main Line soon afterwards, by West Ruislip station (which also happens to be the end of the Central Line). After crossing a roundabout the route reaches a T-junction on the A4180 in the centre of Ruislip.
The B466 multiplexes north along the A4180 for a short distance before turning right at a mini-roundabout to regain its number and its eastward direction. It goes through Eastcote Village where it meets the B472 at a mini-roundabout before skirting the edge of Eastcote House Gardens. At the far end it turns sharply left before going over the Metropolitan Line and ending on the A404 at a double mini-roundabout in Pinner Green.