The preliminary design of the Thetis class was by Y-ARD (Yarrow Admiralty Research Division) according to Olsen and Storgaard (1998)

Olsen, G. & S. Storgaard (1998): Flådens Skibe og Fartøjer 1945-1995, Marinehistoriske Skrifter, Copenhagen, Denmark, 317 pp.

Regards
JS

Cheers! I thought I had read that some where, could not find it on my book shelf.

Wanshan – Flex is a danish system of exchanagble boxes and weapons, but the actual design of the vessel is not flex.