With Barrow he scored a club record 351 tries and kicked 20 goals in exactly 500 appearances from 1943–57. He scored 50 tries in his last season, 1956–57, another club record. He retired after Barrow's Rugby League Challenge Cup Final defeat by Leeds in 1957, one of three Wembley appearances he made with the Cumbrian club during that decade.
Lewthwaite's Testimonial match at Barrow took place in 1956.
On the international front he travelled to Australasia with Great Britain in 1946 – the famous "Indomitables" tour, named after the vessel on which they sailed, HMS Indomitable. He top-scored with 25 tries on that tour despite not making the Test team. He also won one England cap.
Jimmy Lewthwaite represented Cumberland.
Challenge Cup Final appearances
Jimmy Lewthwaite played Right-Wing, i.e. number 2, in Barrow's 0-10 defeat to Wigan in the 1951 Challenge Cup Final during the 1950–51 season at Wembley Stadium, London on Saturday 5 May 1951, played Right-Wing in the 21-12 victory over Workington Town in the 1955 Challenge Cup Final during the 1954–55 season at Wembley Stadium, London on Saturday 30 April 1955, in front of a crowd of 66,513, and played Right-Wing in the 7-9 defeat by Leeds in the 1957 Challenge Cup Final during the 1956–57 season at Wembley Stadium, London on Saturday 11 May 1957, in front of a crowd of 76,318.
He was a natural athlete and represented Cumberland at rugby union and association football as a schoolboy, as well as winning a medal in the All-England Schools Athletics competition at the age of 13. He moved to Woodley, near Reading, shortly before turning 15 to work at an aircraft factory but later relocated to Barrow to take up an apprenticeship at the town's shipyard. He continued to excel as a footballer and had trials with Blackburn Rovers and Preston North End before switching to rugby league with Barrow in 1943, making his first-team début against St. Helens in April that year. He also managed to play golf around the district, after he slowed down from rugby.
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- "1950-1951 Challenge Cup Final". wigan.rlfans.com. 31 December 2011. Retrieved 1 January 2012.
- "Barrow at greyhoundderby.com". greyhoundderby.com. 31 December 2011. Retrieved 1 January 2012.
- "Barrows all time leading try scorers". barrowrlfc.com. 2011-12-31. Archived from the original on 2014-01-16. Retrieved 2012-01-01.