A man's been arrested in relation to an assault outside a Manukau Denny's restuarant nearly two weeks ago.

George Siaosi was left in a critical condition after he was king-hit out of the blue in the early hours of a Saturday morning.

He's now in a serious-but-stable condition.

Police are thanking the public, the media and local businesses for their help in the 18-year-old's arrest.

He will appear in the Manukau District Court today.