It's strange, the way they have "renovated" the viaduct. As I must have mentioned before, one of the reasons it is a remarkable thing is that it was one the first ever poured-concrete structures, made in 1888. The fancy brick exterior is merely a cladding. Yet all that seems to have been done is that the brick parapet has been repaired (you can see the repointed brickwork in the photograph) and the old railbed cleared and given a tarmac surface. I suppose someone must have checked the structural integrity of the edifice -- is the underlying concrete sound? -- but there is no evidence of it.
It has now become a rather pointless but safe (?) elevated path to nowhere, popular with parents with buggies and small children on trainer-bikes. This is fitting, in a way, as the viaduct was originally constructed because one of two railway companies which were building competing lines from London to Southampton went bust when it reached Winchester. To save the truncated line to the east of St. Catherine's Hill becoming a highway to nowhere, a link was made from that line to the one to the west of the hill -- hence the viaduct, built to get the linking track over the River Test. Now that only the successful line survives, the viaduct is a large brick-clad anomaly in a field next to a motorway slip-road.
View (much cropped) from St. Catherine's Hill, over the Hockley
Viaduct and M3 motorway towards the Winchester Park and Ride