It is usually with the managing director and a sales manager and possibly the technical manager. You do a telephone interview first to go over your cv and they ask questions on this, if they like you they will invite you to an in person interview at their cambridge office. At the in person interview you will be expected to carry out a 10-20 min presentation on a particular topic related to what the company does. Then they go over your cv and ask a couple questions on that such as technical experience in physics/engineering and why you want the role and why you would be suitable for sales.