On the side of the cab, it says 'Saddingtons, Coal & Smokeless Fuels, Garden St. Thurmaston'. The label on the back of the photograph says that it was taken on 12 September 1978 and "still working 1984" - whether this means the lorry or the company I am not sure.
A Google search for 'Saddington coal merchants Thurmaston' turned up the following piece in the 24 July 1931 issue of The London Gazette:
The 21 September 1937 issue of the London Gazette informs us that Walter Saddington made a separate application for discharge from bankruptcy which was suspended for six months, and he was then to be discharged as from 19 February 1938.
A quick check of the 1911 census seems to indicate that Harry and Walter were the sons of William and Bertha Saddington of Thurmaston, Leicester. More work to be done here.
If anyone can let me know who would have been driving that lorry in 1978, I'd be very grateful.