Sorry for the five day delay II. I was referring to the directional signal beneath the main signal. My memories are they were angled to indicate the direction the train was authorised for which is not the case here.
That was a very old 1950/1960s standard. All signals are installed at 90° to the track they apply to unless a curve is involved, in which case they will be angled so that they are focussed approximately (but not always) to the signals
AWS▸ (Automatic Warning System) magnet which is generally positioned 183m on the approach to the signal.
I suspect jdw.wor was referring to another angle - whether the upper light is to the left or right of the lower. I think in the past the two lights of some of these mini-signals (associated, position-light, or whatever) were thought of as miniature route indicators. But that too went out long ago, and now the direction of any points is indicted by a tiny arrow or (as in this case) be a "theatre-type" indicator. In this case its "S" is presumably for siding - there's only one so there is no need to say which side.
It's all in the current version of the official signals picture-book:
RSSB▸ Handbook 521 "Signals, Handsignals, Indicators
and Signs" Issue 5 (beware - several old issues are also Googlefindable).