Here are a couple of blurbs from The Times on Hilverum.
"Originally there were nine holes of which Mr. Abercrombie was largely responsible; now another nine holes have been added by Mr. Colt, so that the golfer is confronted with delightful blend of subtlety and boldness that recalls the most pleasing features of New Addington and Swinley Forest. Again the course has been cut out of the wood, the fairways stretching down long aisles, where pine trees predominate, but where there is not quite so much restriction as The Hague." ~~ 7/17/1929
"Hilversum, like the Hague, is cut out of pines, oaks, and birches, but it is not so circumscribed. Like the Hague it is on the short side in actual yardage, being just under 6000 yards, but it plays longer by comparison and its scratch score, also of 74, is even harder to accomplish. As with all Dutch courses it abounds in the most beautiful natural features which obviate an excess of made bunkers, allowing the architect to ensure such as do exist being dominating in character. There are two distinct loops of nine holes, the older made by Mr. Abercrombie, the newer the work of Mr. Colt. Together they make 18 of the most interesting testing and subtle holes imaginable, where the thinking and accurate golfer is 'in clover,' although he will look in vain for it on the new part, which is the freehold property of the club. On this part the greens and fairways are undoubtedly the best of any links course in the Netherlands, and one doubts if there is finer turf, so free of weed, so admirably uniform in texture anywhere." ~~ 8/4/1931