This a short, nine minute film to commemorate the construction of the Travolator between the Bank and Waterloo stations in London to supplement the long walk required of City commuters and nicknamed The Drain. The otherwise exemplary box of DVDs, The British Transport Film Collection does not identify any credits. For the only time that I am aware of, the credits of a BTF production were merged in a democratically alphabetical list without designation of jobs.
Can this be any other than David Watkin? It is an odd carelessness to get his name wrong. Apart from its historic value, and evidence of the balance of surface and underground excavation and construction, 
the film culminates in a sequence of the opening of the Travolator by the Lord Mayor, uneasy in his ceremonial role pressing the button as hordes of merry-makers gather to be the first to use the facility.
There seems a deliberate attempt in the editing to stress the Commoners ribaldry at the face of Officialdom, all set in a most brilliantly lit white tube, an apotheosis of reflected light.