I found this place mentioned in Denis Bray's book, where he describes time spent as Tai Po's District Officer in the 1950s:
The District Officer lived in a fine little bungalow called The Lookout. The government had bought this from the estate of a judge who had been executed by the Japanese during the war. It had no mains water but water was supplied from an intake on a stream which ran strongly all the year round. This not only supplied the house, the overflow went to a swimming pool in the garden. The view from the spacious lawn over Tolo Harbour, with scattered stake-nets for fishing, to the Pat Sin mountain range was spectacular.
Thanks to Phil for giving me the location of the building on Google Earth, and also for the pointer to its entry in the AMO's survey of historic buildings:
The Tai Po Lookout was built by Lawrence Gibbs, a British civil engineer, as his residence in the early 1900s. It is remotely located on a peak near Lookout Link in Tai Po. It was private residences for different owners before it was used by the Japanese during the World War II. In 1947, the Lookout was sold to the government and was turned into a residence of government officials. After the last resident of the Lookout moved out in 1996, it became a Residential Centre for terminal AIDs patients. It has been leased to a private residence by Government Property Agency since 2000.
It's currently a Grade II listed building, with the recommendation to increase it to Grade I.