Four directors of Horizon Technology, headed by chief executive Mr Samir Naji, have realised almost £20 million (#25 million) after selling shares to institutional investors.

More than three-quarters of the shares were sold by Mr Naji, whose stake in Horizon fell from 55 per cent to just under 51 per cent. His remaining stake is worth #304 million (£241 million) at yesterday's #9.50 placing price.

Since Horizon floated on the Dublin and London markets last December, the shares have risen strongly and from the #1.64 flotation price they reached a high of #14.00 in February before falling back to trade in a recent range between #9.00 and #11.50.

A 5 per cent equity placing last February eased some of the liquidity difficulties in the shares, but with just 25 per cent of the shares on the open market institutional investors have found it very difficult to trade Horizon shares in size. Of the institutionally-held shares, about 60 per cent are held outside Ireland.

Mr Naji said: "Through this placing we are providing additional liquidity in the stock to satisfy demand following the company's announcement of its full-year results. The vendors continue to be significant holders of stock in the company and have no plans to dispose of further stock in the foreseeable future."

Horizon has a market value of #630 million (£540 million), more than 10 times the rated value of the company in December 1998. The placing of the directors' 2.5 million shares yesterday by Davy and NCB, increases the free float to more than 38 per cent. This is still a low free float and market sources believe that further placings are possible to increase the free float further.