Found this info that clarifies the procedure for those already registered as historic tax free @Bhubesi When the rules change on 20 May 2018, vehicles won’t need an MOT from the 40th anniversary of when they were registered. You can check the date the vehicle was registered online. Example If a car was first registered on 31 May 1978, it won’t need an MOT from 31 May 2018. You won’t have to apply to stop getting an MOT for your vehicle. However, each time you tax your historic vehicle (even if you don’t pay a fee), you’ll have to declare it meets the rules for not needing an MOT. https://www.gov.uk/government/news/mot-changes-20-may-2018
Interesting because i've got a tax reminder for the 31st may 2018 and it says "this vehicle will need an mot". It was registered in 1969
