The end of Paddington's platforms eight and nine was certainly the place to be when it came to a vantage point, and the "spotters" are certainly out in force here in this delightful reminder of how it used to be in those happy days
The unidentified "Castle" (the number ends in 8 or 9 and it is from 82A) has, I think, worked up from Bristol and is backing out under Bishop's Road bridge either to Old Oak or Ranelagh and one young enthusiast by the lamp standard is going to record the event on film , whilst others, complete with their Ian Allan ABC's compare notes.
There was always something convenient to sit on , usually a well placed Porter's trolley, and a group have located such a facility, whilst senior members are content to watch the activities from the platform end.
Happy days!