Jacob Greasley has been practising martial arts for more than 25 years has trained extensively in Japan in the martial arts of karate, jujutsu and swordsmanship. He attained the rank of 5th Degree Black Belt, in jujutsu in Hiroshima, Japan in 2019 and 5th Degree Black Belt in Shito Ryu karate in Kobe, Japan in 2023. He is the Chief Instructor of the Jikan Kai association and is a registered Member of the Japanese Budo Association in Tokyo.

In addition to his martial arts achievements, he is ex-British soldier and a former door supervisor (bouncer) with many years of experience in security and personal protection.

In his professional life he is a senior engineer and doctoral researcher in the field of Machine Learning and the Internet of things.