Senior Instructor at Urban Krav Maga North & East London/Rolling Elbows Concept (R.E.C.) Founder David "Hydra" Kyriacou teaches you in 90 Seconds how to knock someone out. DO NOT TRY THIS AT HOME!! www.hydrakravmaga-ldn.co.uk www.urbankravmaga.com / urbankravmaganortheastlondon