The style of the double decker bus indicates this photo was taken in early 1950s. In looking at recent street photo views, I noted the several low level buildings just beyond the clock building were later merged together to make one continuous structure. There was no gap between them and the clock building but I cannot tell if there was a path connecting the two.
These low level buildings are gone, the ground was bare in late 2016 and a new high rise is likely there by now. What is interesting is that they chopped off a good part of the clock building for the re-development, and you can see the cut in street view photos at likely the original exterior wall. It would be interesting to know if the company expanded its office area, or the new neighbour built butting against its wall.
Photo source: uwants.com - post #1772 by user 4rex - http://www.uwants.com/viewthread.php?tid=14833421&page=119#pid212384491