I passed my test first time with Mark last year. Firstly, he is extremely proficient and knowledgable, and really has a knack for explaining things. Combine this with patience and cool-headedness, and you have the recipe for the perfect teacher.
Mark instantly made me feel at home in the car, and made sure we repeated things I hadn't quite grasped, even when I didn't yet know I hadn't got them (he's very observant and good at spotting where one needs to make an extra effort). Under his expert tuition I passed my test with ease after only twenty-odd lessons, which I understand is very quick indeed.
I could not recommend Mark highly enough, particularly for anyone who's a little nervous about driving and wants an instructor who'll help them be efficient with their time in the car. Mark is also a really cool guy, with a cracking sense of humour, so his lessons were above all fun, and I always found myself looking forward to them!