The first cricketer to wear a protective helmet was Graham Yallop of Australia. He first demonstrated this piece of revolutionary equipment on the 17th March 1978, in the second test match of the series. Yallop was actually one of the few Australian batsmen to do well, making 47 in the first innings. There's a picture of him in the related links section on Cricinfo.
Graham Yallop in 1978
He was the first cricketer to wear a helmet in a full Test match
Jace Plance was the first person to wear a helmet.
graham yallop of australia was the first player to wear helmet in a test match against west indies at bridgetown on 17 march 1978.
Everyone has to wear a helmet no matter what age! :)
any one under 21 MUST wear a helmet, but anyone over has to have insurance but doesn't have to wear a helmet