Imtech, which has a turnover of around £4bn and 28,000 staff, said that it was paying five-times Smith Group’s current operating profit, which in the last filed accounts was around £1.6m.

Smith Group UK employs around 270 staff out of offices in Preston and London and turns over around £60m.

It designs and installs building services such as air conditioning, heating and fire control systems and counts Willmott Dixon, Lend Lease and Carillion among its main customers.

Since 2003, Imtech has been on the acquisition trail in the UK and recently bought maintenance specialist Inviron.

After the acquisition of Smith Group, Imtech revenue will total over £460m in the UK.

Stephen Smith and Martin Brook, joint managing directors of Smith, said: “We are pleased to have been acquired by one of the leading technical services providers both in the UK and Europe.

“We see this as providing a platform for the continued development of Smith Group UK  and are eagerly looking forward to broadening our services to our clients, both as Smith Group UK and with our fellow companies of Imtech in the UK.”

Jim Steele, general manager, Imtech UK & Ireland, said: “The acquisition of Smith Group UK fulfils our strategy to provide our clients with a full technical services offer across all geographic areas.

“The requirement of clients and main contractors for solid, financially strong M&E contractors supported by innovative technical engineering practices is ever increasing in the competitive market we operate in.