Lord Mount - very well put.
As another London copper of 23 years, and as a dog handler, I frequently work in close partnership with the Met ASU and can confirm that they are worth their weight in gold in terms of speed of response and reduction in officer-hours taken to search large areas. As Jayteeto says, the vast majority of these jobs are never made public.
And as far as:
Police tell him to claim on insurance, as they won't enter the site for a £3,000 trailer.
...then I simply don't believe it. If it
is even partially true, then the victim of the theft should make a complaint.