Wallis gained his first employment working for the "Skegness Standard", leaving after six months to work for the "Worksop Guardian" as part of a National Council for the Training of Journalists (NCTJ) scheme, during which he also studied at Richmond College of Further Education in Sheffield. Having passed his NCTJ exams, Wallis worked for "The Northern Echo" (in its Durham office) before becoming a senior reporter for the "Manchester Evening News". At this point in his career, Wallis became a Crime Reporter, giving talks to police officers on police-media relations, whilst also freelancing for "The Sunday People", progressing from the paper's Manchester desk to its London office. Wallis later said: "During this time I travelled extensively throughout Britain and the world as both a hard news reporter and as an investigator. This included lengthy periods in the USA, the Middle East and Northern Ireland during the 'Troubles' - where I was hospitalised after being caught up in a particularly violent riot. I spent six months in Argentina during the Falklands War including spells in Buenos Aires and Commadorio Rivadavia, the invasion base of the Argentinean Junta. I also spent time in most countries in Europe and the Mediterranean". Wallis then became the paper's Chief Investigative Reporter, responsible for conducting investigations into "murders, show business scandals, corruption, crime in general, drugs, spying and politics".