Jac Holmes was angry when we first met him. He hadn't been in Syria for very long but he already felt the experience had changed him. It wasn't hard to understand why.
He'd left his job as an IT worker and his home in Bournemouth at just 22 and been involved in some of the fiercest fighting against IS in Syria.
He'd seen sex slaves and the markets that IS had set up to sell the women; he'd seen fellow fighters killed and discovered the phones left behind by the militants filled with amputations and torture. He'd come up against a resilient, violent enemy determined to die.
:: British sniper who fought IS killed by landmine in Raqqa
He was fired up with fury about what he saw as the Western apathy to what was happening in Syria - and the former painter and decorator was hell-bent on doing whatever he could to help those who were fighting the cruelty of IS.
He was also reticent towards the media, suspicious and mindful that the foreign fighters like himself often attracted attention from journalists whilst their colleagues in the ranks of the Kurdish fighters, did not.
Nevertheless, this quietly spoken young man spoke with fervour and a conviction that he was doing the right thing.
He spoke angrily at what he perceived to be the British Government's inaction towards the events in Syria.
This, like so many of the foreign fighters we spoke to, appeared to be what had driven them to flee their homes and lives and take up arms against the Islamic militants.
"Daesh [another name for IS] is not a problem just for Syria - or Iraq", Jac told us, "but for the world".