Khan is fighting a man who was planning to be a spectator in April

Bull had seats for the card featuring Joe Calzaghe's fight with Peter Manfredo in Cardiff on 7 April, with Khan, 20, the main support attraction.

Instead, former Central Area champion Bull will meet Khan in the ring.

"My partner and I are due to be married in July and she gave me a present of tickets for the show," said Bull.

Interview: Amir Khan

"We were going to have a nice weekend in Wales and support the British boxers.

"It's amazing how things work out because now I am going to be getting into the ring and there is going to be a spare ticket next to my missus. It feels like I have been handed a lottery ticket."

I couldn't believe it when this opportunity came up and it is one I intend to grab with both hands Khan's opponent Steffy Bull

Bull, a part-time teaching assistant for children with special needs, has a record of 24 wins from his 29 professional fights.

He called time on his boxing career following his last bout in October after a fight with unbeaten local prospect John Fewkes fell through.

"When negotiations fell through to fight Fewkes I felt the chances were not going to come," said Bull.

"I have had a long career in boxing and I have never really got the big breaks.

"I felt maybe at 30-years-old, when I'm about to get married and I've got a family, it might be the end.

"I couldn't believe it when this opportunity came up and it is one I intend to grab with both hands.