When did the S&T branding appear on BR departmental wagons?

Certainly such marked stock was around in the 1960's, particularly with ex bogie coaching stock converted fpr use as either electrification overhead installers vehicles or mess and riding vans and cable carriers. The modernization period of electrification involved the S & T to focus on relay and cabinet wiring along with "dressing" posts with multiple aspect colour light heads on big jobs involving other departments. Smaller jobs had S&T gangs operating as mobile teams using road vehicles, also large instals such as gantry brackets and the such structures would have been undertaken by the Civil Engineers Dept meaning the S&T took responsibility for testings and commissioning. In the olden days of the post LMS peeriod equipment wagons would have used such as Boplate or Borail trolleys to carry large mechanical installations to site and these vehicles would have been marked as DCE stock.