Slight pedantic point about the linked article – it states the tunnel was re-opened for double deck trams in Feb 39 – think this is a typo, it closed Feb 1930, and re-opened (in double deck mode) Jan 1931 following rebuilding by the London County Council.
By 1939, London Transport was well into the process of replacing London’s trams with trolleybuses (had WW2 not intervened, London’s last tram would probably have run in 1942-3) – there was one prototype trolleybus built with an offside door for use in the Subway, http://www.flickr.com/photos/44996480@N02/4795558257/ – although clearances were very tight, and it would also have involved trolleybuses having to tow a trailer to take power from the conduit slot – at least through the subway. There was some discussion about them doing so over Westminster Bridge and round the Embankment also, to avoid the need for overhead wires.
Slight pedantic point about the linked article – it states the tunnel was re-opened for double deck trams in Feb 39 – think this is a typo, it closed Feb 1930, and re-opened (in double deck mode) Jan 1931 following rebuilding by the London County Council.
By 1939, London Transport was well into the process of replacing London’s trams with trolleybuses (had WW2 not intervened, London’s last tram would probably have run in 1942-3) – there was one prototype trolleybus built with an offside door for use in the Subway, http://www.flickr.com/photos/44996480@N02/4795558257/ – although clearances were very tight, and it would also have involved trolleybuses having to tow a trailer to take power from the conduit slot – at least through the subway. There was some discussion about them doing so over Westminster Bridge and round the Embankment also, to avoid the need for overhead wires.