How can I become an M.O.T. tester at a garage...and how can I train to be one?

In the early days of the M O T the garage owner or authorised examiner put your name down when he was confident in your ability.The test was very basic brakes,lights,steering,tyres,over the years the test became more and more stringent and testers had to attend a theory test at the HGVtesting station and then a practical test at your place of work,if you already work in a testing station they would train you there