The route starts at the Hook interchange with the A3 and A243. There is a fork junction with the A3, so that southbound A3 traffic can turn off onto the A309, and A309 traffic can join the A3 northbound. The A243 has a roundabout over the A3 just a little bit East of the fork. However, the westbound entry slip from the A243 doesn't ever join the A3, but only the A309, and similarly the eastbound exit is from the A309 only, not from the A3. For a long time, after the Kingston bypass was built but before the Esher bypass was, what's now the A3 south of here didn't exist, and the A3 was along what's now the A309, and indeed this stretch of A309 is still called the Kingston bypass. Although dual carriageway, it was never upgraded to the same standard as the rest of the Kingston bypass, perhaps because they already knew that an Esher bypass would be required.
About half a mile after the split from the A3 is a roundabout with Claygate Lane, a residential street of little importance, which these days doesn't go to Claygate unless you're on foot. A little further on is a signal-controlled crossroads in the middle of Hinchley Wood. On your right is the Hinchley Wood pub (which nearly became a McDonald's). Continuing on the A309 there's a bridge across the railway (the Guildford "new" line, i.e. that used for Waterloo to Guildford via Cobham services) adjacent to Hinchley Wood station, and about half a mile after that you get to the famous Scilly Isles roundabout. Presumably the name is because it's supposedly silly (or maybe because of the several small islands); it actually works fairly well, and was probably better when it was built. Originally the main road was the A3, which came where we've just come from, and went on to Esher on what's now the A307; with two less important side roads - the A309, and the A307 to Kingston - on the same side, it made sense to put them on a little extra bit on the side so that the through traffic had a straighter route. Now I suspect that a fairly high proportion of traffic goes straight across, sticking on either the A307 or A309.
The A309 passes under the South Western Mainline railway, goes past a golf course on the left, and continues as a fairly wide (two-lane, with plenty of white paint) road past Esher college. There's a roundabout with the B364. After another mile, there's a bridge across the River Mole, with the Hampton Court branch of the railway alongside. Very shortly after this is the rather large Hampton Court station building on the right. There are two turnings on the left close together: the B3379 and the A3050. Both will take you to Walton, but the B3379 (for the first 700 yards, and then the B369) is the slow way via Molesey. Immediately after the A3050 junction, the A309 crosses the Thames on Hampton Court Bridge. Very soon after that it temporarily comes to an end at a roundabout with the A308. The A308 goes left or straight on here; Hampton Court palace is on the right.
Hampton Court – Strawberry Hill
Tim Lidbetter writes:
The A309 is one of three roads that pass invisibly through the Royal Parks (the others are the A3214 in St James's Park and the B351 in Richmond Park), because what do we see in Teddington, on the other side of Bushy Park? The A309 again (starting as a useless multiplex on the B358)! It finally gives out by the Thames on the A310 at Strawberry Hill.
A short multiplex along the A308 ends by the Lion Gate to Hampton Court Palace, where the Chestnut Avenue heads north through Bushy Park. There is a one-way loop around the Diana Fountain, after which the Avenue continues. At the far end it goes through the Teddington Gate to reach a T-junction; to the right is the B358 and the A309 reappears as the road to the left.
Since August 2020, however, through traffic has not been allowed through Bushy Park as the Royal Parks authority has sought to eliminate commuter traffic from the park. This was originally experimental, but was made permanent in March 2022. Traffic now must continue along the A308 and turn left just before it reaches Hampton Wick onto the B358.
The B358 turns off at the next mini-roundabout after which the A309 continues northwards away from the park into the centre of Teddington. It meets the A313 at a roundabout after which there is a short multiplex across the Kingston Loop Line into the start of the High Street. The multiplex ends at a mini-roundabout and the A309 continues north, initially parallel to the railway line then bending more easterly at the B360 junction. After passing St Mary's University College the road ends at a mini-roundabout on the A310 a short distance from the River Thames.
History
Originally the A309 started on the A3 (now A307) just to the west of the Scilly Isles roundabout and headed north along what is now the B3379 to join its current route just before crossing Hampton Court Bridge. The road was moved eastwards onto its current route (a new link road) in the 1930s and then extended south along the former A3 when that road was diverted to bypass Esher.
The gap through Bushey Park and the northern extension to Strawberry Hill are unchanged since 1922.