As an undocumented migrant in France, Mamoudou Gassama knew it was best to keep his head down, to not draw attention to himself.

But when he spotted a young child dangling from the balcony of a fourth-floor Paris flat he felt he had to act.

In that split second, Gassama, 22, did not think of himself or the threat of discovery and deportation back to Mali.

Instead, in an extraordinary feat of strength and bravery that has earned him the nickname "Le Spider-Man", he pulled himself up from balcony to balcony, before lifting the crying four-year-old to safety.