How much have you retained of the grammar you learnt at school? I’m guessing not a lot – at least not in a formal sense. ‘Dominant clauses’, ‘past participles’ and ‘future perfect tense’? If you can define all those you probably don’t need to read on. Strangely, although most of us left a lot of grammar behind when we walked out of our final English exam, there are other English lessons which have stuck fast – despite their being wrong or now out-of-date.