After excelling in karting — winning the British Junior TKM Championship in 1989 — Plato progressed through Formula Three and Formula Renault before finding his niche in touring car racing. His breakout moment came in 1996 when he dominated the Renault Spider championship to claim the title.
Plato entered the BTCC in 1997 with the prestigious Williams-Renault factory team after winning a head-to-head test against Gianni Morbidelli and Jean-Christophe Boullion. He took pole position for his first three races in the Renault Laguna and won two races as a rookie, finishing third in the championship behind team-mate Alain Menu. He remained with Williams for 1998 and 1999, finishing fifth in the standings both years.
Plato joined Vauxhall for 2000 and again placed fifth in the championship. The 2001 season proved decisive: new cost-reduction rules reshaped the competitive order, and Vauxhall fielded the strongest package on the grid. Plato fought a contentious campaign against team-mate Yvan Muller and clinched the championship when Muller's car caught fire at the final round.
Harbouring ambitions to compete in NASCAR, Plato stepped away from the BTCC in 2002 to race British ASCAR stock cars for XCEL Motorsport, finishing third in the championship in a Ford Taurus. He returned to the BTCC paddock in 2003 as a driver coach for SEAT before rejoining the grid full-time in 2004.
Plato led SEAT's factory effort from 2004, guiding the new Toledo to race wins from its debut season — securing seven victories and third overall in his first year with the Spanish manufacturer. He finished fourth in 2005 as SEAT introduced the León model, then mounted a sustained championship challenge through 2006 and 2007. His 200th career start came at Croft in 2006. In 2007 he fought a season-long battle with Fabrizio Giovanardi's Vauxhall that went to the final round, with Giovanardi taking the title by three points. Plato was magnanimous in defeat, saying of his rival: "Fabrizio beat us the right way. He is a very worthy champion."
The 2008 season saw SEAT pioneer diesel power in the BTCC. Plato helped deliver the first-ever diesel win in the championship at Donington Park but reliability issues undermined his championship push, and SEAT subsequently withdrew their factory programme at the end of the year.
Following SEAT's exit, Plato signed with the RML Group to drive a privately entered Chevrolet Lacetti in 2009. At the final round at Brands Hatch he won all three races in a single day — only the second driver in BTCC history to achieve the feat — including one victory by a then-record winning margin of 0.015 seconds. He finished the season second overall, five points behind champion Colin Turkington.
For 2010, RML became an official Chevrolet manufacturer team running the Cruze. Plato dominated the second half of the season and secured his second BTCC title by winning round 29 at Brands Hatch, equalling Andy Rouse's record of 60 career victories in the process. In 2011 he claimed his 61st win at the opening round to set a new all-time record, eventually finishing the season third in the standings.
Plato spent three seasons with Triple Eight Race Engineering's MG KX Momentum Racing team (2012–2014), finishing third in the championship twice and second once. He then moved to Team BMR in 2015, where he came within four points of a third BTCC title. In 2016 he recorded his 500th career race start, marking the occasion with a win at Knockhill aboard a Subaru Levorg. Further wins at Knockhill followed in 2017, but a crash at the 2017 season opener caused chassis damage that affected his car's handling for much of the year. The 2018 campaign with BMR was difficult following a switch to a new engine supplier; his sole podium was a second-place finish in the opening race at Croft.
Plato joined Power Maxed Racing in 2019 to drive the factory-backed Vauxhall Astra, claiming a win in the final race of the season. After the team sat out 2020, he returned in 2021 but mechanical problems limited his results to 14th in the standings. His final BTCC season came in 2022 with BTC Racing, where he finished 17th overall with a single podium at Snetterton, ending a 26-year association with the championship.
Plato's BTCC record stands in a class of its own: 97 race victories, two drivers' titles, and 13 top-three championship finishes across a career that stretched from 1997 to 2022. He remains the championship's all-time leading race winner by a substantial margin. Away from the circuit, Plato maintained a parallel media career as a co-presenter on Channel 5's motoring series Fifth Gear from 2004 onwards, and published his autobiography in 2019. In 2026 he launched Plato Racing Team RML to field a Mercedes-AMG A35 in the BTCC, extending his connection to the championship as a team owner.