Before Police and Criminal Evidence Act 1984 (PACE), there were no Custody Sergeants. They were called Bridewell or Station Sergeants depending on what Police Force or part of the country you were in. Also, the name "Custody Suite" was not introduced until 1984, again due to PACE.
The form of caution used at the end includes "it may harm your defence if you do not mention, when questioned, something which you later rely on in court". However, that wasn't introduced until 1994.
As Bacchus is hanging off the ledge, trying not to fall, all he has to do is let go, since the fall is short and he would land on his feet.