The 20hp car was discontinued for 1906 and cars listed for the year comprised the 24hp introduced the previous year, the magnificent new six-cylinder 6,975cc 36hp and the 14hp with its advanced sohc engine (updated with HT coil ignition instead of the previous year's LT magneto).
Tom Thornycroft drove a 14hp in the 1906 TT, but the car suffered from technical problems.
Like its 24hp stablemate, the 36hp car had T-heads, and cylinders cast individually. Specific power outputs were very low in the early part of the last century, and the six-cylinder car's meagre 36bhp from nearly seven litres now seems almost unbelievable!
Thornycroft traded on its marine engineering reputation when it introduced its six-cylinder car, claiming, probably rightly, that its experience of building six-cylinder marine engines underwrote the design of the new automotive "six". Also, Thornycroft thought it useful to remind car buyers of the firm's wider technical competence, mainly in marine engineering, e.g. war vessels, shallow draft vessels, yachts, motor launches, steam wagons, petrol wagons, passenger vehicles, steam engines, marine motors, generator sets for lighting, water tube boilers, marine propellers, and other products. Modern-day experts would probably dismiss the relevance of some of Thornycroft's other activities, by claiming that there was no "synergy" between cars and marine engineering! In this, the experts would almost certainly be wrong.
HRH Princess Christian was evidently well pleased with her 1905 Thornycroft car, because the firm's 1906 brochure, Thornycroft Touring Cars, proudly proclaimed that "As a special mark of appreciation of the excellent running qualities of the Thornycroft car supplied to their order, Their Royal Highnesses Prince and Princess Christian of Schleswig-Holstein have been graciously pleased to favour us with a Royal Warrant of appointment as motor manufacturers". Princess Christian took delivery of a 1907 30hp Limousine on 26 November 1906 as vehicle no. 643. This is the only delivery against which Princess Christian is mentioned in the Thornycroft sales register, and any other cars supplied to her were presumably accepted on her behalf by agents, whose names would be in the register.
The 24hp car and, possibly, the 36hp in the 1906 model line-up were fitted with LT ignition, but the 14hp car's HT coil system was the shape of things to come. However, for about the next 25 years, vehicle manucturers became wedded to the HT magneto, which had the advantage of being a compact, self-contained spark generator with a built-in make-and-break and distributor. By the mid-twenties about 65 per cent of cars in the UK had magneto ignition. However, coil ignition eventually won the day on, and the HT magneto is now all but extinct on cars.