They looked like students in pen written t-shirts that helped people on the tube and accompanied people home. Their tshirts said tube angels.
They may have been an off shoot of the oxford street hare krishna's.
I remember some barefoot bloke and a woman talking to us and accompanying us to our tube stop, we would have been 14/15/16 and this would have been the mid-late 90s.
We used to go Leicester Square to Seven Sisters.