By the mid-1980s, Lewis had begun to write for television series; his writing credits include episodes of Perfect Scoundrels, Taggart, The Bill, Wycliffe, Inspector Morse, Kavanagh QC, The Ambassador, Monsignor Renard, Playing the Field, Without Motive, The Last Detective, Murphy's Law, Spooks and Lewis.
In 2021, Lewis recorded an Audio Commentary for the first episode of The Bill that he wrote, entitled "Forget-Me-Not", alongside actress Lynne Miller (WPC Cathy Marshall), released on The Bill Podcast Patreon Channel.
Lewis wrote Grace, which is based on the bestselling books by author Peter James.
[5] In 1993, Lewis won the Writers' Guild of Great Britain TV - Original Drama Series Award for Between the Lines.
The award was shared with the other writers of the show at the time, J.C. Wilsher, Rob Heyland, Steve Trafford and Michael Russell.