When Santander bought Abbey National nearly four years ago, rival bankers said it was only a matter of time before Spain's biggest bank did a second deal to extract maximum benefit from the acquisition.
Alliance & Leicester was top of most people's lists because it was big enough to give Santander scale and the scope for cost cuts.
Emilio Botin, Santander's chairman, said in February that he was no longer interested in buying A&L after conducting talks in December. But the wily operator is understood to have kept the bank under review and chose Friday – with A&L at its lowest ebb – to make his move.
His return to the deal should have come as no surprise. Santander ended an initial round of talks with Abbey only to return and claim its prize a few months later.
Santander has sidestepped much of the fallout from the collapse of the US sub-prime market and the resulting credit crunch thanks to Spanish central bank restrictions on structured credit investments and the bank's focus on retail banking.
The bank has forecast profit for 2008 at more than €10bn (£8bn), a record, as growth in Brazil and elsewhere in Latin America makes up for a sharp economic slowdown in Spain. It has doubled its presence in Brazil with the acquisition of ABN's business there but still makes about half its profit in Spain and the UK, where property bubbles have burst and the economic outlook is bleak.
The A&L deal will boost Santander's share of the UK savings market to 8.1 per cent from 5.9 per cent and give it 12.9 per cent of the mortgage market, up from 9.3 per cent. A&L's commercial banking operations will also speed up Abbey's long-held desire to expand in business banking.
Antonio Horta Osorio, who runs Abbey, said: "We face difficult times and should be prudent. The strategic logic of this deal is absolutely compelling, there is a huge fit."
Mr Botin is a shrewd deal maker who has built Santander through acquisitions into one of the world's top 10 banks. He has emerged largely unscathed from the acquisition of ABN Amro last year while the bosses of Royal Bank of Scotland and Fortis, his partners in the break-up deal, have been pilloried for overpaying. The Santander chairman won applause in November when he agreed to sell ABN's Antonveneta Italian business for a profit of £1.7bn just weeks after the takeover was completed. The deal left Santander with spare cap-ital that he is now using on A&L.
But some analysts, while acknowledging Santander's opportunism, say its foray into the UK has detracted from its distinctive appeal for investors.
Simon Maughan, a banking analyst at MF Global, said: "They shouldn't have bought Abbey because it has diluted returns for the group. Focusing on Brazil or Mexico would have brought much higher returns. But you can see this as a necessary evil to build some scale and boost returns."