Are there any specific instructions for photographers on the
Underground? I was standing at the Baker Street station (Metropolitan
line platform) and tried to make photo of the local junction (at the
moment when train was passing it) - I was approached by two policemen
and told to stop photography and delete existing photos (they even
checked that the photos were deleted) as no photography allowed on the
Underground anymore due to the threat of the terrorism.

Is it true?

P.S. I was standing in the location permitted for the passengers and
photos without flash. Even more, I shot more then 10 stations during
the week, and this is the first incident of the kind (even though in
many locations I stood right next to station staff).