For train times, prices & how to buy tickets, just see https://www.seat61.com/Turkey.htm. The video showcases an epic 3-night train journey from London to Istanbul, right across Europe to the edge of Asia, distilled into just 12 minutes... The route takes you via Paris, Zurich, Zagreb, Belgrade & Sofia, with an evening in Belgrade and a day between trains in Sofia. Quite a bit has changed since the video was made, so just see https://www.seat61.com/Turkey.htm to learn about the latest train times, fares & tickets between London and Istanbul.