Design and engineering group Scott Wilson plc has agreed to buy a mechanical and electrical building consultancy in a bid to strengthen its underground infrastructure services.

The London-based group has exchanged contracts to acquire Terence Lee Partnership in a deal that could be worth as much as £1.3 million.

On completion, which is expected to be 6 June, £1 million in cash will be paid. Up to £300,000 has been deferred and is due in two equal annual tranches if agreed conditions are met.

The companies have worked together on several London Underground projects in the past six years, and the proposed acquisition is part of Scott Wilson’s strategy to strengthen its underground infrastructural operations.

Scott Wilson executive chairman Geoff French said the deal will help the group to take advantage of growing international demand in the sector.

London-based Terence Lee, which was founded in 1978, made a £200,000 pre-tax profit in the 12 months to November last year from an £800,000 turnover.

Scott Wilson offers professional services to the transport, property, environment and natural resources sectors. It has more than 6,000 employees in a network of 80 offices in the UK, China, Hong Kong, India, the Middle East, Eastern Europe and Southern Africa.