For a bank that is so big and that has apparently been so successful in the past five years in building up its huge investment banking and markets business, HSBC is remarkably coy about how it makes its money.

We know, for example, that last year the group made a whopping $19bn in pretax profits. And we know that under Stuart Gulliver's tutelage before he was promoted last year to group chief executive, HSBC's global banking and markets business has grown into a giant cash dispenser that generates exactly half of these profits.