On the left we see the Hilsea Lines, probably in 1903, just after the electrification of the tram route up to the top of Portsdown Hill was completed.

Originally built as a simple earthwork rampart, to defend Portsea Island from attack from the north, Hilsea Lines were reinforced and extended in the 1860s, as part of the defence plan that included the building of the Palmerston Forts in the Solent and on Portsdown Hill.

Even before those extensions and improvements, such was the suspicion of the French in certain quarters that when the London and Brighton Railway Company extended their tracks into Portsmouth, they were made to build a small fort to protect the access tunnel that was cut through the rampart to allow the railway to finally come onto Portsea Island. Did the government have sentries searching the trains for French insurgents, I wonder?

This picture is almost certainly of the remains of that railway fortification; since the mid-nineteenth century, of course, the railway has been slightly re-routed and most of the interior of the Hilsea Lines has been blocked off, for safety reasons.

On the right, we can see that the original moat found a far better use when the Lines were finally declared obsolete ...

By the 1930s, when the construction of the Eastern Road had created a second road route onto Portsea Island, it was obvious that the Hilsea Lines served little or no purpose from a defensive point of view.

Eventually, it was decided to turn the area close to Portsbridge into a leisure facility, with Hilsea Lido opening in 1935 and the old Hilsea Lines moat utilised as a boating lake.

With the addition of the rose gardens, a play area and the miniature railway, the site remained popular long after the war years, and the Blue Lagoon bar and restaurant served many different functions; however, the city council never seemed entirely happy with the Lido, possibly because outdoor pools require far more maintenance and are only usable during the warmer summer months.