Just before the UK went into lockdown in March, HSBC banker Charlie Nunn found himself in charge of $1.4 trillion (£1 trillion) worth of assets. The bank had merged its money-spinning wealth and personal banking divisions, Nunn was in control of both, and the plan was to triple the number of billionaire clients in China.

But wooing the wealthiest people in the world is no longer top of Nunn's to-do list after Britain's biggest high-street lender Lloyds surprised the market by unveiling the low profile banker as its next chief executive.

Instead of quietly focusing on the mega-wealthy, Nunn will now be dealing with the aftermath of the coronavirus pandemic and Brexit from one of the most high-profile and heavily scrutinised jobs in Britain.

While insiders say his resignation is a major blow to HSBC, outside of the banking world he is little known. City bets were instead on the likes of Unicredit's chief Jean-Pierre Mustier, RBS's ex-boss Stephen Hester and former HSBC chief John Flint, Nunn's predecessor. Others expected an insider, such as finance chief William Chalmers.

"This comes as somewhat of a surprise," Citi analyst Andrew Coombs wrote in a note to investors. "With a new chairman [Robin Budenberg from January], and now confirmation of a new CEO, there will be questions about future strategy."

Flint can see why his protégé got the role. In his view, the former McKinsey consultant is a tech whizz, which is exactly what big banks such as Lloyds are looking for. "Charlie may well be the most technology competent banker of his generation," he says.

The challenges facing Lloyds are very different to those that confronted outgoing boss António Horta-Osório when he took the reins in 2011.

Back then, Horta-Osório had to steer the lender through the fallout from the financial crisis and back into private hands after its bailout.

Flash forward to 2021 and Lloyds's digital shift is top of its agenda due to cost pressures and changes in customer behaviour. The bank is reportedly interested in acquiring Starling, the online bank, as it wants its technology.

The coronavirus pandemic has accelerated the shift to online and emphasised why Lloyds, viewed as a bellwether to the UK economy, needs to diversify. Amid fears it is too reliant on UK retail banking, the plan is to push into other areas such as wealth management. Nunn seems an obvious bet.

"Nunn’s skill-set suggests that he is likely to maintain Lloyds' existing priorities [such as] diversifying other income, [and] shift to digital," said Citi's Coombs.

That does not mean the road ahead will be smooth.

Although Nunn, a cycling fanatic with four teenage children, will not inherit the same problems as Horta-Osório, he will be battling a whole new set of challenges arising from an unprecedented crisis that has devastated the economy. The issues will be immediate.

"Horta-Osorio was leading Lloyds out of a crisis, yet Nunn will be leading the company as it heads straight into one – with the full impact of the coronavirus pandemic on the economy yet to hit," says Russ Mould, analyst at AJ Bell. "[He] faces a pretty stiff test."