As one of London's most esteemed surgeons, he has wide experience in a range of surgical treatments, including surgery for hiatal hernia, anti-reflux surgery, bariatric surgery, and oesophageal & gastric cancer surgery. Mr Hashemi holds a notable safety record, with over 3,000 stomach and oesophagus operations performed at a zero-mortality rate.

Mr Hashemi has performed a range of 'firsts' in surgery, including the first laparoscopic gastric bypass and first laparoscopic sleeve gastrectomy in North London in 2004 (the sole surgeon regularly performing this surgery in the area from 2001 until 2007) and the first LINX implant for reflux in London in 2013. In 2017, he performed the first ever implant of a LINX device on top of a sleeve gastrectomy.

Mr Hashemi is one of the only 12 surgeons in the UK who can currently offer the LINX procedure as a method of treatment for acid reflux. His significant experience allows him to give a focused, patient-centred approach, tailoring treatment for each individual and their specific needs.

He has an interest in open and laparoscopic hernia repairs and he works as a Specialist Consultant Surgeon at London Hernia centre at the Hospital of St John and St Elizabeth in North London.

Mr Hashemi is actively involved in training, education and research, leading and supervising on a number of research projects. He was appointed as Senior Lecturer to University College London in 2001 and was Surgical Tutor and Lead for Academic Surgery at the Whittington hospital and Archway Campus 2001 – 2007. From 2007 -2010 he was Chair of the Surgery Module Management Group for Surgery Undergraduate studies for University College Medical School.

As well as surgery for the treatment of obesity, Majid provides the full range of services in oesophageal and gastric surgery, including assessment and treatment for patients with various hernia types, oesophageal reflux or motility problems including those requiring revision surgeries.

He regularly performs oesophageal and gastric resections for cancer as part of the team at the designated Cancer Centre at University College London Hospital. He is a firm believer that patients should be involved in all major decisions.

Through his dedication to innovation in surgery, Mr Hashemi established and chaired one of the country's first bariatric surgery services with a multidisciplinary approach, providing patients with 'one-stop' care, diagnosis and treatment from a range of specialties. The establishment of the first bariatric surgery team in North London allowed Mr Hashemi to develop surgical approaches, and provide training for many of today’s bariatric and upper GI surgeons.

He currently is Medical Chair of the Achalasia Action, , and has one of the longest and most extensive experience in the surgical treatment of achalasia in the capital. Mr Hashemi is also an active researcher, and maintains a strong interest in education, having previously held tutoring and lecturing positions at University College and the Whittington Hospital. He is published extensively and is regularly invited to speak at conferences both on a national and international level. He continues to be involved in training for laparoscopic and bariatric surgery, and acts as supervisor for a number of research projects.