Alex Renton attended three traditional private schools. When he was eight he left home and boarded at Ashdown House, a prep school in East Sussex; a feeder school to Eton College.

Within weeks of his arrival he was sexually abused by a teacher. The teacher was never charged or even sacked. He died in 2011, a free man.

The assault, compounded by the physical and emotional abuse so often a feature of boarding school life, has stayed with Alex. And like a great number of the million Britons alive today who attended these institutions, he spent the subsequent years trying to forget what had happened to him there.

Then, in 2014, Alex finally decided he had to face his demons. He wrote a book, Stiff Upper Lip, about public schools and about the experiences he and others had within them. That’s when the emails and letters started pouring in. Former pupils, men and women, from all around the country, shared with him their stories of sexual and physical abuse. The scale was breathtaking.

Now, years later, Alex Renton has unfinished business with Britain’s elite schooling system.

In the first episode of a three part series, Alex returns to Ashdown House, where some of Britain's most powerful figures, including Boris Johnson and the Queen's nephew David Linley, were educated.

From Sussex to South Africa, Alex tells the story of how a group of men, all subjected to horrendous sexual abuse, are still fighting to bring their abusers to justice.

Producer: Caitlin Smith Additional Research: Claire Harris Reporting in South Africa: Nceba Ezra Singapi Sound Design: Jon Nicholls Editors: Gail Champion and Heather Kane-Darling

Photo: Alex at eight years old