The chief executive of Detica was celebrating a £24.5 million payday yesterday after the data security group agreed to sell itself to BAE Systems, Europe's biggest defence contractor, in a cash deal worth £531 million.

Tom Black, who owns 4.79 per cent of the company, is one of seven directors to collect a cash windfall from the takeover.

Detica specialises in data protection work for government bodies and the private sector. Customers include the Ministry of Defence, HM Revenue and Customs, AstraZeneca, the pharmaceuticals company, and Vodafone, the telecoms group.

Colin Evans, the group managing director, will receive £3.97 million if the 440p-a-share deal goes through as planned. A further five directors will share £3 million.

In total, Detica employees own 10 per cent of the group, which was set up 31 years ago to provide software services to companies including Nasa, the American space agency. In 1997 Detica was the subject of a management buyout backed by Candover, the private equity firm.

Five years later it listed its shares on the London market at 80p each. It employs more than 1,500 staff.

Mr Black, a 24-year veteran of the company, joined Detica after a brief stint in national security. Having spearheaded its drive into the commercial sector, he became chief executive at the time of the buyout and led the subsequent flotation. He will stay on at Detica when it is folded into BAE. It is not yet clear how many of the other directors will remain.

BAE has been on the prowl for companies expert in what it describes as the national security and resilience sector for several months. Detica, a market leader in its field, is thought to be the only listed company of its kind and gives BAE immediate scale.

Yesterday's agreed deal comes just over a week after BAE and Detica confirmed that they had entered talks to discuss a potential offer.

The terms represent a premium of 57 per cent to Detica's 281p closing share price on the day before it emerged that talks were taking place.

Detica shareholders will also be entitled to a 2.5p-a-share dividend covering the year to March 31, during which pre-tax profits were £25.4 million on revenues of £203.2 million.

Work for governments in Britain and America accounts for just over 60 per cent of Detica's revenues. Under the ownership of BAE, it will expand further into the US.

Detica's shares jumped 66p to 438.25p after the agreement. However, the shares remained below the 440p agreed price for the takeover, suggesting that shareholders were not predicting the arrival of a third party or a potential auction.

Shares in BAE lost 6.5p, down almost 1.5 per cent at 438.75p. It will pay for the acquisition from its cash reserves.

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