Food Partners, the sandwich maker that began its life in Scotland and employs some 300 staff at a plant in Kilmarnock, Ayrshire, has bought Brambles Foods, one of its main rivals, for £22m.

The Heathrow, Greater London-based Food Partners bought the Brambles business from venture capitalist NBGI in a deal that will allow the seller to pocket more than four times the amount it paid for the business in July 2004.

The acquisition will allow Food Partners to consolidate its position in the market for pre-packed sandwiches.

Industry experts reckon the annual value of this could expand from £3.5bn to £4.7bn as growing numbers of lunchers opt for the convenience of packed food.

Food Partners has achieved rapid growth on the back of expansion of the fast food market and the acquisition of a series of rivals.

Originally named the Sandwich Company, Food Partners was founded in 1997 by three managers who lost their jobs following the collapse of Scottish Pride.

Venture capital firms including 3i and the Belgium-based Pan European Food Fund have backed expansion by the company, whose chief executive, David Kilshaw, is based in Aberdeen.

With plants at Heathrow, Aldershot and Kilmarnock, the company makes more than one million sandwiches a week for clients including coffee shops, the NHS, catering organisations. It has annual turnover of £50m plus.

Brambles was founded in 1990 by John and Lynn Pearce, who retained a stake after selling the business to a management buy-out team backed by NBGI.

The company supplies customers across the UK including hospitals and schools. Sales exceeded £23m in 2006.