Siebe plc became the name of the new conglomerate formed when Siebe Gorman began taking over other firms in the early 1970s, to distinguish it from Siebe Gorman's original breathing apparatus and diving gear core business. Siebe plc was once one of the United Kingdom's largest engineering businesses and was a constituent of the FTSE 100 Index. In 1999 it merged with BTR plc to form Invensys.