Green’s Dictionary of Slang

very, extremely.

1879		Blackburn Standard 24 May 2/1: It’s blessed beastly; yet I s’pose i ought to like it.
1911		E. Dyson ‘Dukie M’Kenzie’s Dawnce’ in Benno and Some of the Push 41: Bring erlong Jumbo someone, ’n’ we’ll blessed soon clear up this gazob.