One, at the Soyo oil fields in Angola, was held by UNITA forces in the civil war there in the early nineties. Connections between him, Simon Mann and Eeben Barlow led to the development of Barlow's Executive Outcomes into the war. He is considered by many to be an innovator of the private military industry and certainly a progenitor of the link between modern business and security teams.
EO was successful and expanded through the nineties. Buckingham's relation to the company has been obscured in a myriad of corporate subsidiaries, relationships and interests. His group of holding companies include stakes in DiamondWorks and logistical companies used by EO and Sandline
Many allege Buckingham was the money behind the idea, perhaps many of the ideas behind Executive Outcomes  and subsequently Sandline. What there is little doubt of is having an army in the oil and mineral industry in Africa benefits the procurement of contracts.
"Mr. Buckingham is the founder of Heritage. Mr. Buckingham commenced his involvement in the oil industry as a North Sea diver and subsequently became a concession negotiator acting for several companies including Ranger and Premier Oil plc. He was previously a security adviser to various governments." 
Resources and articles
- Heritage Oil plc Board, organizational web page, accessed September 20, 2012.