A beginners' guide to tea

How many of us wine-lovers who wouldn't dream of serving a sub-standard wine to our friends are perfectly happy to give them - or serve ourselves - a cup of tea made with a teabag? Like wine, tea is a daunting subject. Many of us, and I include myself among their number, are woefully ignorant about different types of tea, how best and when to serve it and how to partner it with food.