Leigh is a Chartered Chemical Engineer and Chartered QS. He began his career as a Chemical Engineering specialising in filtration technology and control and automation systems before moving across to the commercial arena, initially heading up a tendering department, then a large commercial team working mainly in the water and power industries. Latterly, Leigh was the Commercial Director for a UK operation along with several large joint ventures. In 2015, Leigh set up his own practice, acting as an expert witness, adjudicator, adjudication party representative and consultant/advisor. Leigh has acted in over 250 adjudications.