Mr Allen is a leading consultant urological surgeon with HCA Healthcare and the Royal Free NHS Trust. He completed his urology training in London and further honed his expertise through a fellowship at University College Hospital, specialising in the diagnosis and management of complex urinary tract stones. Mr Allen was appointed as a consultant at the Royal Free Hospital in November 2011.

Mr Allen conducts weekly outpatient clinics, flexible cystoscopy lists, and operating sessions. He addresses a wide range of urological issues, including urinary symptoms, blood in the urine, elevated PSA, scrotal swellings, prostatitis, and kidney stones. His goal is to provide a world-class rapid access clinic tailored to each patient's specific needs.

In addition to his clinical work, Mr Allen is deeply involved in the teaching and training of medical students and junior doctors. His research focuses on the treatment and prevention of kidney stones, an area in which he has delivered numerous international presentations and authored multiple papers.

Mr Allen is proficient in a variety of medical tests and treatments, including flexible cystoscopy, rigid cystoscopy, rigid ureteroscopy, flexible ureterorenoscopy, and supine percutaneous nephrolithotomy (PCNL). He also performs circumcisions, vasectomies, epididymal cyst removals, and hydrocele repairs.

His areas of expertise encompass general and diagnostic urology, renal and ureteric stones, lower urinary tract dysfunction, prostate disorders, haematuria (blood in the urine), and scrotal abnormalities.