Probably the New Territories or possibly on the Island.
Following Moddseys's and Peter's suggestions, and my subsequent comments, I now believe that this photograph was taken on the Tai Tam Road to the North or North East of the reservoir dam. It's very difficult to pin-point the exact spot because the two very distinctive sharp double bends, that look likely, do not match what one can see on the modern Google Earth Street View. However, I have placed the pin on the map in possibly the right place, not very far from the junction of the Shek O and Tai Tam roads at the Tai Tam Gap, which is probably just out of sight behind the edge of the cliff face on Malcolm's photograph. It is thought that the gently rising slope in the background on the photograph is the lower North end of Mt Collinson. The Shek O road would have been running horizontally more or less in line with the far wall. Thanks for the help of several contributors. I hope this is correct! (Andrew S)