South Shields-born Mortensen went to war in 1939 as a teenage wireless operator and overcame an injury—sustained when his RAF bomber crashed, leaving him as the only survivor—to be signed by Blackpool in 1941.

During the war, he scored dozens of goals before making a strange piece of history by switching teams to play for Wales when they needed a reserve during a game against England on 25 September 1943.

[5] Wales' Ivor Powell was injured and had to leave the field and, as England's reserve, Mortensen took his place in the Welsh side.

Wales lost 8–3, and Stanley Matthews later wrote of the game: "Nobody in the 80,000 crowd had any idea that Mortensen was going to change.

[7] In the FA Cup semi-final of 1947–48, Tottenham Hotspur were leading 1–0 with four minutes remaining when Mortensen equalised from a cross from Stanley Matthews.

Mortensen scored two more goals in extra-time as Blackpool reached the final of the FA Cup for the first time.

In the final, Blackpool took an early lead from a penalty against Manchester United before Jack Rowley equalised.

[11] In injury time, Bill Perry converted a Matthews cross to seal a 4–3 win for Blackpool.

In the book The Great English Final, author David Tossell states that only since the publication of the FA Yearbook two months later, which awarded Mortensen with all three goals, that the hat-trick became accepted as fact.

[13] In the Charity Shield match at Highbury against Arsenal,  Mortensen put the FA Cup winners ahead.

He scored another hat-trick, this time in a 1948 British home championship match as England beat Ireland 6–2 at Windsor Park, Belfast.

In a fixture dubbed Match of the Century, England lost their long unbeaten home record against foreign opposition.

[6] On 18 November 1989, Mortensen led the Blackpool team out onto the Bloomfield Road pitch for their FA Cup first-round tie with Bolton Wanderers.

Former Bolton Wanderers forward Nat Lofthouse, who faced Mortensen and Blackpool in the 1953 FA Cup Final, led the visitors out.

[19] Mortensen is mentioned with admiration in the song "1966 and All That" on the 1986 vinyl EP The Trumpton Riots (incorporated into the 2003 CD re-release of the 1985 album Back in the DHSS) by the indie band Half Man Half Biscuit, who call him "The Tangerine Wizard"[Note 1] and "The Jesus Christ of Bloomfield Road".

[8] On 23 August 2005, a statue of Mortensen was unveiled by his widow, Jean, and former Blackpool teammate Jimmy Armfield in front of Bloomfield Road's new North Stand, which now bears his name.

[25] Mortensen was inducted into the Hall of Fame at Bloomfield Road, when it was officially opened by Jimmy Armfield in April 2006.