"This is a real Houdini act," said one veteran Amstrad follower. "To get out of the commodity hand-held mobile phone market, pass go and collect pounds 80m is stupendous."
Shares in Amstrad closed 21.5p higher at 221.5p, valuing the company at pounds 262m and Mr Sugar's 35 per cent stake at pounds 92m.
"Amstrad felt it had taken Dancall as far as it could," Mr Sugar said. "Realistically, the Amstrad philosophy has not lent itself to running a business in the long term."
Since Dancall was bought for pounds 6.3m from the receivers in 1993 Amstrad has invested pounds 10m, but the company remained in the red in the face of cut-throat price competition for digital handsets from the likes of Nokia and Motorola.
Mr Sugar said interest in Dancall increased last year after merger talks between Amstrad and rival consumer electronics group Psion collapsed. Interest intensified after Dancall launched what it claimed was the world's first truly international cellular mobile phone at a trade fair in Hanover last month.
"The virtues and potential of Dancall have never been fully appreciated by the shareholders or the financial institutions," Mr Sugar said.
Andreas Nobis, a board member of Bosch, said the German group would retain the entire workforce of Dancall and would increase its plant capacity to over 2 million telephones a year.
Analysts said plans to return some of the cash raised from the sale to investors confirmed suspicions that Mr Sugar, who tried to take Amstrad private five years ago, was slowly liquidating the company.
At the end of December Amstrad had a cash pile of pounds 112m and following the Dancall deal it will be left with Viglen, which sells computers direct to the public, and a 66 per cent stake in Betacom, the consumer electronics subsidiary.
Analysts are concerned about where Amstrad's next blockbuster product is coming from. There is talk of a user-friendly Internet browser being developed while Amstrad is in line to share in a pounds 500m order for BSkyB's digital set-top boxes.
Amstrad, a former FTSE 100 company, was a darling of the stock market in the late Eighties. But the company slipped into heavy losses in the Nineties as recession and an influx of new competitors drove computer prices down.
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