In Biggles Buys a Watch, Roderick McDew was an ex-RAF squadron mate of Biggles who had turned to smuggling watches. During the war, McDew had served in Biggles' squadron at Karga Oasis in North Africa (see Biggles Sweeps the Desert). Biggles remembered him as "that rare thing, a dishonest Scot." According to Flight Sergeant Crane, another squadron mate, Biggles had McDew posted as a "no-use scrounger".

After the war, McDew had obviously lived up to that reputation as he had taken up the selling of smuggled watches. His typical modus operandi was to ask for a loan, offering the watch as security. He would then fail to redeem the watch, which was as good as having sold the watch to the unfortunate lender of the money. Almost every doorman in London had "bought" a watch and was eager to sell it away, all describing the "seller" as a "slick-looking type with red hair, who speaks with a slight Scotch accent"--a description which fitted Roderick.

However McDew went too far trying to sell it to Flight Sergeant Crane as Crane knew his identity and went on to tell the story to Biggles. Gaskin later filled Biggles in on how the watch racket worked: paying duty on an imported watch would more than double its cost. By smuggling them in, the watches could be sold cheaper than regular ones but yet fetch a tidy profit. Watches were small and easily carried in by air.

Checks with Crasher Doyle at Air Intelligence revealed that there was an unidentified aircraft which had come in from the North Sea towards the South side of the Moray Firth for three consecutive months always on the night of the full moon. Cross-checking revealed that this was near the croft of McDew's father at Balburnie. Biggles visited Mr McDew, Roderick's father and learnt that Roderick was in the habit of visiting him monthly and taking long walks across the heather in the direction of a place called Dubh Chtais.

Biggles staked out the moorland using the directions given by Mr McDew and caught the helicopter bringing in the watches. McDew ran off with the bag of watches and was later arrested at a roadblock on the road south.