On paper, WestLB does not look like the type of institution that might naturally engage with Islam. A medium-sized German bank, it has traditionally earned a living by lending to German manufacturers – and then, more recently, moving into the private equity and derivatives world.

But earlier this year the bank unexpectedly earned a striking accolade: it underwrote a £225m package of Islamic finance to support a leveraged buyout of Aston Martin, the racing car group, by a group of Middle Eastern investors.