It is the second time the flamboyant Mr Buch has become involved in a quoted company since he walked away with pounds 25m after selling Blenheim to Lord Hollick's United News & Media for almost pounds 600m last year.
He recently took a 29.9 per cent stake in BBB, a small design and marketing company which he now chairs.
Shares in BBB Design have risen sharply since Mr Buch's arrival, rising from a low of 16p to over 80p before settling back at last night's close of 65p.
Mr Buch seems to have worked a similar trick at Somic where his investment is already showing a paper profit of pounds 330,000.
In a statement Somic said Mr Buch, together with a family trust and a company associated with him, had bought 464,000 shares in Somic, representing 21.9 per cent of the company.
Somic added that it had appointed Mr Buch and three other directors as non-executives of the company.
Together the four new directors hold 34.4 per cent of Somic. All these share deals were made on 27 March.
Richard Blackburn, who will continue as executive chairman and managing director, yesterday sold a 9.2 per cent stake in Somic at 78.6p, raising pounds 153,000 before costs. Mr Blackburn retains a 7.3 per cent interest in Somic.
In the year to March 1996 Somic blamed depressed demand for upholstery yarns for a 25 per cent drop in pre-tax profits to pounds 232,000 on sales 8 per cent higher at pounds 4.5m.
Mr Buch was unavailable for comment yesterday, though he indicated after the Blenheim deal that he wanted to return to the City, albeit in activities unrelated to exhibitions.
Mr Buch was at the centre of a protracted five-month bid battle for Blenheim, which also received rival bids from publishers Reed International and VNU.