Hi, I had mine a few weeks back. Just to shed some light for you. The medical consists of a blood pressure check, colour blind test, sight test which as you suggested was the letters on a wall test, this is done with your glasses on (if required) and then a few minutes later without. They then check your BMI. Also there is a hearing test and drugs & alcohol test. They also go through any pre -existing conditions which may affect you working in a safety critical role. All in all about 30 minutes, nothing too strenuous and should be your final stage of recruitment before getting your start date. HTH