I also went over the barrier and explored the concrete emplacement close up. Would not have liked to have been there in the 60s without ear defenders.
There is also an earlier gun emplacement for defending the shipping channel approaching Pompey which is why it is called Needles Battery. And Tennyson down is also very nice, the view across Alum Bay and across to Bournemouth and the south coast is also glorious. Many reason to go that way rather than the sweet factory and glass blowing.