How did it start?
After Bradley Lowery, a Sunderland supporter, was diagnosed with Neuroblastoma, a terminal form of cancer that mainly affects children under five, Sunderland invited him to be a mascot for their match at home to Everton.
Fans of both sides sang 'there's only one Bradley Lowery', Lowery received a round of applause in the fifth minute and a banner reading 'we're with you, Bradley' was held up around the stadium.
Lowery was ecstatic, telling a local newspaper, "This has been amazing. I got to meet Jermain Defoe, who's my favourite and everyone said my name. Thank you everyone."
In December 2016, Lowery was back again at the Stadium of Light for Sunderland's match against Chelsea.
He went into Sudnerland's dressing room pre-match and went straight for his mate, Defoe.
It was a special day for Bradley who also showed Diego Costa how to take a penalty while meeting the whole Chelsea squad.
His penalty would go on to win the BBC's Match of the Day's Goal of the Month award.
In January Everton invited him to be a mascot for their match with Manchester City at Goodison Park.
With Manchester City losing 4-0 that day, Pep Guardiola had little to smile about - except meeting Lowery.
In February, Sunderland players paid a visit to Lowery in hospital, with Defoe's heartwarming gesture going viral.
Defoe explained how the amazing moment happened and how Lowery is "in his prayers every night."
The England match
After three years away from international football, England coach Gareth Southgate recalled Defoe to the national team squad. No one was more excited than Lowery.
Of course, by now Defoe wouldn't go to Wembley without his best mate Lowery.
Captain Joe Hart allowed Defoe and Lowery to lead out the England team, giving Lowery a moment he'll, and all those watching, will never forget.