Inspired by Andrew's excellent conversion - and prompted by an observation that I didn't have an 'S-Boat' in my collection, I decided to make a model of HMS Splendid.
This was a Swiftsure Class submarine that preceded the Trafalgar Class.
With notes from Andrew (many thanks ) the hull was shortened by 7mm, the upper rudder was also cropped and the single vents on the hull sides of the Trafalgar were replaced by two smaller vents per side.
The finished model.....
Comparison between Trafalgar and Splendid.....
More photos here.
Ken