Iron man star Robert Downey Jr praises eight-year-old 'true hero'

Iron Man star Robert Downey Jr has posted a new video praising a terminally ill Scottish boy as "the true hero".

The actor appears with Aaron Hunter and members of his family, explaining Aaron's condition and appealing for donations for a charity supporting research into ROHHAD.

Previously Downey has been filmed jumping in muddy puddles as part of a campaign raising awareness of the condition which only affects about 100 people worldwide.