Anyhow, I suspect Jaber told Assad that the attention span of Mail readers is quite short so he'd have to give very compact replies to her hardball questions. That could explain his frenetic hand-waving while he spoke lol -- and his tone, which I think was not so much angry as rushed. She shoehorned 22 questions into a six-minute interview and Assad answered them all.
SANA has posted the complete transcript and video of the interview with Arabic translation but the Daily Mail also has the video minus the Arabic script, and their headline and Jaber's report on the interview are more fun to read than SANA's prose:
"President al-Assad to Mail on Sunday: UK publicly supported White Helmets that are a branch of Al Qaeda, US and UK existence in Syria is invasion"
Daily Mail headline
"I use chemicals? Prove it! Syrian President Assad brands gas attacks 'fake news' and calls Theresa May a 'colonialist and a liar' in astonishing face to face interview"