London City Mission leader Graham Miller and his wife were attacked on the streets of south-west London, where they regularly evangelise, after Mr Miller challenged some children for abusing a cafe manager near the railway station.
The attack took place in front of the couple's young daughter. The couple were repeatedly punched in the head from behind and the woman was knocked to the ground. As she lay on the floor, the children continued to beat her and passers-by had to pull them away.
In recent months, the Earlsfield area near Clapham has seen a dramatic increase in small gangs of young people, often girls, intimidating passers-by and turning violent when confronted. Several muggings and robberies have also been reported in the area, which is otherwise popular with families and London commuters.
Miller says he won't give up evangelising to the troubled youngsters.