Paul Foley's boss will take temporary charge of Aldi's UK business following the shock departure of the UK MD this week, but the appointment is not expected to be permanent.

Armin Burger, promoted to oversee Aldi Süd's international expansion in 2007, will be very different from the PR-friendly Foley, being known inside Aldi as 'the silent tycoon'.

But a long-term move to the UK would be a step down for Burger, according to Planet Retail research director Matthias Queck, with the UK's £1.5bn sales representing 3% of Aldi's global sales. A UK retail headhunter added: "Burger has an excellent reputation and is on Aldi's fast-track to the top."

Foley's departure was "mutual", according to a terse Aldi statement, adding: "Mr Foley is widely credited as challenging and changing traditional market perceptions to establish Aldi as a leading brand offering high-quality and best value products. Aldi's plans for future development remain unchanged."

But Foley's exit was clearly sudden, with Foley not believed to have another job lined up. He was unavailable for comment as The Grocer went to press.

Aldi had been feted as the big winner of the recession, posting sales growth of 25.4% in the last quarter of 2008 [TNS].

But as the big four supermarkets responded to the threat of the discounters with new 'discounter brands', aggressive price cuts and the same single-price promotion mechanics used by Aldi, sales growth slowed to 8.3% in the 12 weeks to 12 July. And with its store estate growing by 35 to total 415, rivals were suggesting like-for-like sales had fallen as much as 0.9% in the last year.

Industry insiders were shocked at Foley's departure, with speculation varying. One senior industry source said Aldi may have decided to rein back the speed of expansion.

"Opening a new store every week is expensive. Perhaps the directors felt growth prospects in the hard-discount sector in the UK were not as sustainable as Foley appeared to think they were."

Another felt Foley's style was at odds with the reserved and secretive culture at Aldi's German HQ.

"We have been amazed at some of the things Foley has been saying in the press," said one German retail expert. "In Germany they would never have been allowed to say the things he has."

Another source claimed the letter sent to suppliers last month demanding a 5% cut in prices will have angered head office, especially as it led to bad publicity.

"That was not a very Aldi thing to do," said one international supplier. "Aldi negotiates hard, but then sticks to contracts in a fair way. It damaged Aldi's reputation. Most suppliers have given slight reductions but nothing like 5%. It smacked of desperation."