Newsham joined the TOCA support package in 2008, contesting the final two rounds of the Renault Clio Cup UK before committing to a full season in 2009 with Amery Motorsport. He took one race win at Silverstone and finished fifth in the championship.
His dominant season came in 2010 with Team Pyro. Newsham won the Renault Clio Cup UK title with twelve race wins across the campaign, confirming him as the fastest driver in the junior touring car category that year and earning him the step up to the BTCC.
Newsham entered the BTCC in 2011 with Geoff Steel Racing in a Super 2000 BMW 320si. After a difficult opening to the season he switched mid-year to Special Tuning Racing's NGTC SEAT Leon. He immediately showed pace — setting fastest lap on debut with the new team at Oulton Park and taking a pole position for the reversed-grid race at Snetterton. He ended the year fifteenth in the Drivers Championship.
2012 was a breakthrough year. Driving an ex-Triple Eight S2000 Vauxhall Vectra for Team ES Racing, Newsham won his first BTCC race at Snetterton, followed by a lights-to-flag victory at Knockhill — his local circuit. He added six podium finishes in total and scored his first BTCC pole position at Brands Hatch. He finished ninth in the Drivers Championship and sixth in the Independents' Trophy. The BTCC fan base recognized his impact: he received the official BTCC Fans' Driver of the Year award at season's end.
Newsham tested for Speedworks Motorsport late in 2012 and was confirmed for the 2013 season. He finished tenth in the standings, a solid result for an independent-budget outfit.
For 2014 Newsham joined AmD, driving their NGTC Ford Focus. He finished seventeenth overall with a best result of second place.
Newsham signed with Power Maxed Racing for 2015, driving a Chevrolet Cruze. He achieved a pair of fourth-place finishes and ended the year sixteenth in the championship.
In 2016, unable to secure the budget for a full BTCC campaign, Newsham moved to the British Rallycross Championship with Power Maxed. Mid-season he was recalled to the team's BTCC programme for two rounds as a substitute for Kelvin Fletcher, taking a seventh at Knockhill and a ninth at Rockingham before the year ended. He placed twenty-second in the BTCC standings for the partial campaign.
Newsham's final full BTCC season was spent with BTC Norlin Racing in another Chevrolet Cruze. He placed fourteenth in the championship standings. On 9 January 2018, he announced his retirement from the BTCC.
Newsham's career arc — from Clio Cup champion to BTCC race winner operating on independent budgets — tracks a familiar but difficult path in British touring car racing. His 2012 season with Team ES Racing, during which he won twice, secured multiple podiums and earned the fans' Driver of the Year award, remains his career high point. The Knockhill circuit, near his adopted home ground, was consistently one of his strongest venues throughout his BTCC years.