Briton travelled to Ukraine early last year to work as an instructor training the Ukrainian military, according to a statement by Ukraine's SBU. An investigation into the suspect, said to be a former member of the British armed forces, was carried out in coordination with British intelligence, a security source said. SUBSCRIBE to our YouTube channel for more videos: http://www.youtube.com/skynews Follow us on Twitter: https://twitter.com/skynews Like us on Facebook: https://www.facebook.com/skynews Follow us on Instagram: https://www.instagram.com/skynews Follow us on TikTok: https://www.tiktok.com/@skynews For more content go to http://news.sky.com and download our apps: Apple https://itunes.apple.com/gb/app/sky-news/id316391924?mt=8 Android https://play.google.com/store/apps/details?id=com.bskyb.skynews.android&hl=en_GB Sky News Daily podcast is available for free here: https://podfollow.com/skynewsdaily/ To enquire about licensing Sky News content, you can find more information here: https://news.sky.com/info/library-sales