London Midland and Scottish Railway (LMS) Princess Royal Class No. 6203 (British Railways No. 46203) Princess Margaret Rose is a preserved British steam locomotive.
6203 was built at Crewe Works, being works number 253 of 1935, and being the third member of the class and first of the second batch. It was named Princess Margaret Rose after the then five year-old daughter of Albert, Duke of York (later King George VI) and younger sister of Queen Elizabeth II, Princess Margaret Rose.
The locomotive was used to haul the heaviest and fastest LMS passenger trains from London to north and northwest England and to Scotland. During its operational career it was allocated to Crewe North, Edge Hill (Liverpool), Kingmoor (Carlisle) and Polmadie (Glasgow) motive power depots. After nationalisation in 1948, British Railways renumbered it 46203, and it was withdrawn from service in 1962.
After withdrawal, 46203 was bought by Billy Butlin of Butlins holiday camps and became one of two preserved Princesses, the other being 6201 Princess Elizabeth. After cosmetic restoration at Crewe, it was moved to Pwllheli in Gwynedd, arriving there in May 1963. It remained there until 1975 when it departed for the Midland Railway Centre (now Midland Railway - Butterley) in Derbyshire.
Butlin's sold the engine for £60,000 in 1985 when restoration to working order started, being completed in 1990. It then operated on the UK mainline rail network for several years, hauling special charter trains.
It is now based at the Midland Railway - Butterley in Derbyshire and is owned by the Princess Royal Class Locomotive Trust, which also owns another Stanier pacific, 6233 Duchess of Sutherland.