His biggest achievement to date was reaching the semi-finals of the 2018 PDC World Darts Championship where he lost to Phil Taylor.

[3] Lewis competed in his first UK Open in 2012, defeating Steve Farmer and Mark Stephenson before falling to Pete Hudson in the second round.

[4] In August, Lewis beat John Scott and Michael Barnard in the UK Qualifier for the fourth European Tour event of the year, the German Darts Masters,[5] but then lost 3–6 to Richie Burnett in the first round in Stuttgart, Germany.

[7] Lewis finished fourth on the 2012 Youth Tour Order of Merit, but was the highest player who had not already qualified for the 2013 World Championship.

He beat Colin Osborne 6–4, Robert Thornton 6–5, Steve Brown 6–0, Kevin Painter 6–5 and two-time world champion Adrian Lewis 6–5.

[18] His ProTour ranking saw him qualify for the 2014 World Championship by claiming the third of sixteen spots that were available to players outside the top 32 on the main Order of Merit.

[19] Lewis played Raymond van Barneveld in the first round and was beaten 3–0, losing each set by three legs to one as he hit only three of his fourteen darts at a double.

[23] During the rest of the campaign, Lewis was beaten in the last 16 of three Players Championships and qualified for three European Tour events, but could not get past the second round.

[26] Lewis made his PDC World Cup of Darts debut as the-then number two Welsh player on the Order of Merit behind Mark Webster and they teamed up at the 2015 event, but suffered a surprise 5–3 loss to Hong Kong in the first round.

[29] At the World Grand Prix, Lewis survived two match darts from William O'Connor to edge past him 2–1 in the first round and then came from 2–0 down in sets against Michael Smith to win 3–2.

[36] This gave him entry in to the third round of the main event and Stephen Bunting hit legs of 12 and 11 darts to move from 8–7 down to win 9–8.

[37] In the penultimate Players Championship event, Lewis eliminated the likes of Benito van de Pas and Robert Thornton to play in the quarter-finals, where he lost 6–5 to Simon Whitlock.

[38] He recorded a 6–4 win over Jamie Caven in the opening round of the Players Championship Finals, before being knocked out 6–4 by Dave Chisnall.

[46] Lewis then defeated Stephen Bunting 6–2, Danny Noppert 6–1, and Joe Cullen 6–3, before losing to Gary Anderson 6–3 in the semi-finals.

Lewis won the match 4–3, winning the final set and reached the last 16 of the PDC World Darts Championship for the second year in a row.

[50] At the PDC World Championship Lewis played ProTour qualifier Luke Woodhouse in the first round and came back from 2–0 down to win 3–2 in sets.