Campbell came to prominence during a loan spell at Leyton Orient in 1989 when he scored 9 goals in 16 games. Campbell helped see the club to promotion during that season but didn't play in their victorious playoff final against Wrexham as his loan spell had just ended. Orient manager Frank Clark wanted to make the move permanent but Arsenal refused to sell. After a poor start to the 1989–90 season he was again loaned out, this time to Leicester City. However, in the following season he established himself in the Arsenal team, scoring eight times in ten matches during the run-in to the club's First Division title win.