The A351 is the main road across the Isle of Purbeck.
Lytchett Minster - Swanage
The road starts at a roundabout with the A35 to the west of Lytchett Minster and heads southwest though the forest that runs round the edge of Poole Harbour. The road is straight, but slow, and there are several signs campaigning for a bypass. It runs through Sandford, home to numerous camping and caravan sites, and crosses the railway line towards Wareham.
These days, the A351 bypasses Wareham to the west and meets the A352 at a roundabout. It does a right-angle turn here, giving the road an odd V-shape when you look at it on a map.
Personally I think the old road through the town (now the B3075) is much nicer, as you pass right through the historical high street with lots of old buildings, and a view of the priory as you leave the town on the other side.
At any rate, the A351 soon meets up with its old road and carries on into the Isle Of Purbeck (which isn't an island really), an important National Trust area, popular with hikers and kids on field study trips (or at least it was when I was young!). It runs reasonably straight through flat land until it reaches Corfe Castle, where it snakes around the bottom of the hill, with the castle on top. The B3351 turns off here towards Studland and the chain ferry to Sandbanks.
The A351, meanwhile, runs through the village of Corfe Castle and heads down to Langton Matravers, passing along lots of camping sites along the way. From there, it's just a short run towards Swanage before it stops at the seafront. Originally, the A351 ran along the High Street almost as far as the pier but the road has now been rerouted along Victoria Avenue and ends at a T-junction on the sea front.