Stewart answers Tesco SOS

"Er, Alan, we've got a problem. Would you mind starting tomorrow? I’ve had a word with Marc and he says it's OK." That's how the distress call from Tesco to new finance director Alan Stewart likely went yesterday, as supermarket chiefs pleaded with Marc Bolland, his current boss at Marks & Spencer, to let him go two months early.

And his early arrival is crucial for Tesco, a day after the accident-prone supermarket admitted to one of the most embarrassing financial cock-ups in living memory. The share price is in freefall and the phrase "don't catch a falling knife" springs to mind.

Stewart's appointment had been first flagged in July, but he hadn't been due to start until 1 December. However, like chief executive Dave Lewis, in the top job for just three weeks after his own first day was brought forward by a month, Tesco is in such trouble it couldn't possibly continue without a CFO in place.

Talk about out of the frying pan into the fire. An investigation into serious financial incompetence is underway and four Tesco executives - UK business boss Chris Bush and his finance chief Carl Rogberg, plus John Scouler and Matt Simister at the food operation - have been suspended.

But Stewart - also former chief bean counter at Thomas Cook and WH Smith - will need all his experience to deal with this mother of all accounting errors. Tesco overstated its first-half profits by £250 million - hardly small change - and will now make just £850 million in the six months to 23 August 2014 rather than the £1.1 billion it confidently predicted just three weeks ago.

"There is both upside and downside risk to this forecast, but until the investigation is complete, we simply cannot know what the full year impact might be," said Deutsche Bank.

Tesco shares are down again Tuesday at 197p. One analyst said yesterday the shares might be worth just 165p. That's looking quite realistic while the investigation is ongoing. Tesco has suffered huge reputational damage and there's now a serious concern about what else Mr Lewis and his team night uncover.

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