The family owners of Clark ­Eriksson, the specialist project engineering consultancy based in Falkirk, are in line for a multi-million pound payout after accepting an "out of the blue" offer from a ­Cheshire entrepreneur.

Engenda, formed only five years ago by Runcorn-based Les O'Hare after he sold his family engineering firm to Bilfinger Berger, has paid an undisclosed sum to acquire Clark Eriksson which will retain its identity and management team.

James Toner, 62, who founded the business 30 years ago, and his wife Alison, company secretary, between them own 96 per cent of the shares, while managing director Scott McMartin has a 2.5 per cent stake. The other shareholders each with 0.5% are finance director Corinna Toner, 39, Rik Toner, and technical director Wallace Aitken, 66.

Mr McMartin, 46, said: "There has never been a for sale sign outside the door, it was out of the blue, the company approached us directly based on one of their directors knowing us from a previous employment, and knowing what we could do."

Clark Eriksson employs 35 directly and 22 in contracted providers, and has grown steadily on the back of buoyant demand for its project engineering services in the pharmaceutical, petrochemical, oil and gas, and agrochemical sectors.

Mr McMartin said agrochemical companies in particular had been busy devising new products, responding to the need to maximise global food production from scarce land resources.

"We have been in a growth cycle for the last four or five years, with strong growth in turnover and profit," he added. The £142,000 shown as accruing in last year's profit and loss account was an under-estimate of its profitability, and the group would go forward on a debt-free basis. The accounts show the business had a shareholder value at the year end of £1.2m.

Mr McMartin said the main challenge for the company last year had been the delay to its design contract for Dart Energy's coal bed methane project in Airth, Stirlingshire, which it won two years ago, securing employment for 15 people in its head office in Falkirk. It is hopeful of winning further work during the construction and commissioning phase, but McMartin said planning consent was still awaited.

The Scottish group's clients are largely in the central belt of Scotland, though it has tackled projects in Wales, Spain and the US. Mr McMartin said Engenda was focused on the M62 corridor and had no presence in Scotland.

Mr Toner, executive chairman of Clark Eriksson, said: "Becoming part of the Engenda group is seen as a great move for us as it will not only give us financial support to further expand our business, but also opens up new routes to market and will give us access to Engenda's high quality workforce."

Lee Foundation, managing director at Engenda, said: "We are particularly impressed with Jim and his company and their 'can-do' approach which matches our ethos at Engenda perfectly. The location in one of Scotland's major industrial areas is also seen as ideal for our continued growth in the UK."