In article ,
Tim Roll-Pickering wrote:
I've seen them a few times at Liverpool Street (tube) but they invariably
hang around by the barriers and ask to check people's tickets. Far better to
deploy them at ungated stations.

They are a semi-regular feature of Finchley Central (and Woodside Park,
I believe).

--
I don't play The Game - it's for five-year-olds with delusions of adulthood.