There were a few of those at the show yesterday (I really should have taken some photos). I didn't know production of the P5B and the P6 overlapped (is that correct - my first car was a 15 year old 1966 2000 P6 with 45,000 miles on the clock).
Interesting article - thanks for sharing.
Edit: ChatGPT says yes:
The **Rover P5B** was produced from **1967 to 1973**. The "B" in P5B stands for the Buick V8 engine that was used in this model.
The **Rover P6** was produced from **1963 to 1977**. It was also known as the Rover 2000, 2200, or 3500, depending on the engine size.