Hasdell is considered by many to be a pioneer of mixed martial arts in the United Kingdom, particularly in the 1990s, when he drove a great deal of innovation in the field.

[4] Hasdell promoted the first professional mixed martial arts events in the UK[5][6][7] and helped develop many of the standards within the British MMA scene of today.

Hasdell's professional and competitive career spanned over 20 years with almost 100 bouts in kickboxing, mixed martial arts and submission grappling.

He fought Paval Rumas for the ISKA European light-heavyweight full contact title and lost by split decision after 10 rounds.

This bout was only one week removed from originally receiving the cut in a Thai boxing match in Arnhem, Netherlands against Perry Telgt.

Still ranked no.1 in Britain,[13] Hasdell fought for the European title on 22 January 1994, against Bob Schrijber at the Olympic Stadium in Moscow, Russia.

[17] On 15 April 1995, Hasdell fought undefeated American fighter Curtis Schuster for the ISKA world super-heavyweight Muay Thai title in Paris, France.

[18][19] On 3 September 1995, he became one of the first British fighters to compete in K-1 when he fought South African Duane Van Der Merwe at K-1 Revenge II in Yokohama, Japan.

[24] On 15 October 1995, Lee Hasdell promoted a kickboxing event in Milton Keynes, England which featured three shootfighting contests.

[25][26] On 18 February 1996, Hasdell made his shootfighting debut for Rings Holland at Kings of Martial Arts against Dutch Thai boxer and multiple time world champion Andre Mannaart.

[20] The tournament featured fighters from the United States, Israel, Spain, Netherlands, Nigeria, France and Italy, all representing eight different martial arts.

[29] Hasdell went through to the final with two knockouts over American Jeet Kun Do practitioner Scott Dobbs and Italian Judo and Karate champion Paolo Di Clemente.

Hasdell returned to Tokyo two months later to compete in the Rings light-heavyweight tournament for the divisions inaugural title and lost to Masayuki Naruse in the quarter-finals by submission.

[36][37] On 5 October 1997, Hasdell promoted his first official mixed martial arts event; the first in the United Kingdom, called Total Fight Night.

He would also feature on the card and defeated Dutch karate champion Peter Dijkman by rear naked choke, winning the vacant U.T.F super-fight heavyweight shootfighting title.

Just over a week later in Utrecht, Netherlands he beat Dutch fighter Dave van der Veen by knock-out in the second round, securing his first victory in Rings Holland.

Hasdell received a yellow card for an illegal punch and failed to knock out Namekawa after landing multiple knee strikes, losing the contest by decision.

[45] The following month, Hasdell faced Dave van der Veen for a second time at Total Fight KRG 5 in Milton Keynes, England.

[47] In 2000, Hasdell was awarded his blackbelt in Ju Jutsu and personally invited by the Prince of Abu Dhabi, United Arab Emirates to compete in the ADCC Submission Wrestling World Championship on 1 March 2000.

[49] Hasdell returned to mixed martial arts when he travelled to Moscow, Russia on 29 April 2000, to compete in the IAFC – Absolute Fighting Championships.

In the first round, Hasdell lost to IAFC champion and eventual winner of the tournament Mikhail Avetisyan due to ground and pound.

Hasdell was then scheduled to face British fighter James Zikic on 11 March 2001, at Millennium Brawl 2 but pulled out due to an eye injury he received in training.

In August 2001, Hasdell was given an award from Akira Maeda in Japan for his hard work, dedication and contribution to the martial arts worldwide.

[53][54] Lee Hasdell resumed his mixed martial arts career on 24 April 2004, at Pain and Glory, held at the NEC in Birmingham, England.

Hasdell lost again by rear naked choke at 1:34 of round 2 in what would be his final professional mixed martial arts bout to date.

[61] These events produced and featured fighters such as James Zikic, The magical Dexter Casey,Bobby Razak, Paul Cahoon, Gary Turner, Ian Freeman, Lee Murray, Mark Weir, Valentijn Overeem, Wataru Sakata, Hiromitsu Kanehara, Yasuhito Namekawa, Jess Liaudin and Danny Batten.

[63]After relocating from the Sanctuary Music Arena to Planet Ice in Milton Keynes, Hasdell claimed; "We managed to sell 3,000 tickets.

When other promoters started springing up around the U.K., all the councils went running to Milton Keynes and basically carbon copied all their documentation",[64]Hasdell also insisted that the sport is adequately controlled[65] and have an amazing safety record.

[66] Hasdell's events were featured on many News programs such as LWT Nightlife, Trevor McDonald's Tonight programme on 22 July 1999 and also appeared on Johnny Vaughan's The Big Breakfast show on 15 March 2000.

In 2002 and 2003, Hasdell promoted the UZI-Cage Combat Evolution series, two mixed martial arts events held in a Cage.