Vandals and poor maintenance ensured the area was poorly lit, encouraging further vandalism and discouraging cyclists and pedestrians. The Councils claimed the lights are regularly inspected and maintained. This must mean once every other year, since that's how often any significant number of them worked before...
The City and County Councils at last decided to improve the subway,
and are working to a plan for spending £40,000 over 5 years: murals, seats, lighting,
anti-vandal measures, more plants and so on.
Funding has to come from the two councils plus the private sector.
Work duly started in mid-February: almost all vegetation was removed. Nothing more happened till the end of the month, when new lights were installed in the tunnels. On 8th March new plants started appearing in the flower beds and the burst of work seemed to be finished by mid-April, the final act being to remove the two cement (anti-vandal) rubbish bins.
So for the moment the area is well-lit and when the new plants grow to the sizes of the ones removed, it'll look a lot better, except for all the rubbish lying about as there aren't any bins.
There's still no proper sweeping, with broken glass lying around for between one and two weeks typically.