These two roads formed the original route out of Fareham to the north, although North Hill is clearly more geared towards serving Park Lane.
As its name suggests, Old Turnpike was once a toll road, and it formed the main road out of town to the north at the time - appropriately enough called North Road, although that name is rarely referenced. Until the 1950s maps have it down as 'Old Turnpike Road'. In the 19th Century Wickham Road opened, taking a more difficult course that cut the corner between North Road and North Hill. When this happened, the turnpike moved from the top of the hill to the bottom, sitting in the middle of the junction and serving what is now Old Turnpike and Wickham Road, charging people to use both. It sold refreshments too, and now lives on in spirit with the Turnpike Garage on the same site.
The arrangement couldn't have lasted long because trains made the turnpikes uneconomic and they were taken over by the council.
Several resources claim that all this happened in 1872 (slightly out of our coverage area, but bare with me, this is interesting after all), but maps from before then have the new road marked on, so quite what the correct order of events was I'm not sure. Letting the first few customers go free doesn't sound like a 19th century thing to do.
A number of houses existing on the south-east end of the road were built to serve people working in factories and foundries. The Tollgate is a new estate on the site of the former Turnpike Works, which produced upholstery and sausages. From about half way up, these change to 1940s (developed only when the land was sold), and Furneaux Gardens was built in the 1960s using a brownfield site formerly a tobaccopipe manufacturer.
At its northern end, The New Inn (later The Turnpike Pub) dates back to the 18th Century, but closed in the 2000s, and is now apartments. Beyond this was a post office, but it didn't last long in to the 20th Century. Around here is the original turnpike.
Turning right at what is now a signalised crossroads (a very recent change), we come to the key section of the exit route. North Hill was also a turnpike, but the name didn't stick because it old name is still relevant. The hill which it takes its name from is relatively steep and was a challenge to early vehicles, both motorised and horse-drawn, and large vehicles would usually require several people to dismount in order to speed up the climb. By the time they reach the top, most people would be too tired to argue about the charge, and consequently the turnpike was thought to be very profitable.
At the top was Uplands Cottage. Along the hill is a large pottery, which grew to become one of the largest and most successful in Fareham, which used clay that had been mined close to Highlands Road. It was particularly well known for producing pottery and drain pipes. The smoke from the kiln here would frequently blow around the surrounding area, a nuisance in the early motoring era, particularly along Kiln Road.
In addition to the cottages and potter's houses at the top of the hill, more houses were added at the bottom at the start of the 20th Century. Having closed in the 1960s, in the 1970s the ancient North Hill House and pottery were replaced by houses to form West Downs Close. This incided with the opening of the M27, so some of these had large gardens which took them down to the motorway boundary. For a short time there was an engineering works, which was subsumed by the motorway.
At the bottom of the hill, Wickham Road was plugged in to the existing layout (which can clearly be seen as a straight line), originally creating a simple split. With the opening of the motorway, and dualling of a short section of Wickham Road, the layout was changed so that Wickham Road clearly took priority, with North Hill being a right turn. In the early 1990s, with the opening of Furze Court, this became a roundabout.
A new, unnamed cul-de-sac was added at the bottom of the hill in the late '80s on what was a former clay pit.
This will all change if Welborne ("Whiteley II") is ever built. The roundabout will be replaced by traffic lights and, in a surprisingly sensible idea, North Hill northbound (downwards) will flow non-stop on to Wickham Road. Everybody who normally turns right here will have to rat-run down Old Turnpike.