Barely a day goes by at the moment without excited predictions that new digital technologies are set to revolutionise trading and capital markets. But it's the banks that are using tech to transform their high street operations that are really boosting the bottom line.

In an era of low interest rates and fierce competition, banks are finding it hard to expand their revenues. The key to growth — and crucially, to growing faster than the economy in general — is to cross-sell new products and services to existing high-street customers. And the key to profit is doing so at the minimum cost.