Ell, a former carpenter who was born in Merriwa in the Hunter region in New South Wales, founded Leda Group, a privately owned property development company in 1976. The company's head office is located in Sydney; and it has Business interests in Queensland, New South Wales and the Australian Capital Territory. Included in Ell's property portfolio are residential developments at Pimpama, Queensland; and at Cobaki Lakes, and Kings Forest, New South Wales. He has raised plans to develop a cruise ship terminal, including three liner berths plus a superyacht marina, three resorts and an option for a casino at Tugun. Ell has commercial property interests in shopping centres at Ipswich Riverlink, Victoria Point and Morayfield in Queensland; and at the Tuggeranong Hyperdome in Canberra. In 2012 it was reported that Leda had developed properties worth a total of more than A$3 billion since Ell established the group in 1976.

Ell floated Leda on the Australian Stock Exchange in the late 1980s and privatised the company in 1990.

In 2009 it was reported that Ell acted as a surety for Michael McGurk and provided A$100,000 in bail for firebombing and assault charges against McGurk; with the charges subsequently dropped. Following the 2009 murder of McGurk, Ell issued a statement detailing his Business and personal relationship with McGurk, including an alleged interest in the Crest Hotel, located in Sydney's Kings Cross. Ell had a longstanding dispute with Greens Tweed Shire councillor Katie Milne where he successfully sued her for defamation in the NSW Supreme Court, and was awarded A$15,000 in damages. The defamation action related to an email sent by Milne alleging he had a scandalous association with McGurk.

In 2012 Ell sought and was granted permission by the Privileges Committee of the New South Wales Legislative Council to lodge a Citizen's Right of Reply on behalf of Leda Holdings Pty Limited. The reply related to comments by Cate Faehrmann MLC, a member of the NSW Greens, in the Legislative Council on 9 November 2011. Ell's reply highlighted errors of fact and the distortions contained in Faehrmann's speech. The Privileges Committee ordered that the Citizen's Right of Reply be published.

In 2014, the Business Review Weekly assessed Ell's net worth at A$1.29 billion; and Forbes Asia assessed his net worth at A$1.10 billion. In February 2013, Ell listed for sale a 4,397-square-metre (47,330 sq ft) residential property in Cremorne with an asking price of between A$20 – 25 million. In July the same year, Ell sold his Potts Point penthouse apartment for A$15 million and purchased a non-waterfront house in Bellevue Hill for A$30 million twelve months later. It was reported between 2000 and 2002 that Ell owned a luxury 36-metre (118 ft) catamaran called Leda worth A$15 million.