Green’s Dictionary of Slang

Salisbury Crag n.

(drugs) heroin.

1993		I. Welsh Trainspotting 121: Four weeks n two days since ma last bit ay Salisbury Crag.
1999		I. Rankin Dead Souls 4: ‘Salisbury Crag’ has become rhyming slang in the city. It means scag, heroin.
2012		(con. 1980s) I. Welsh Skagboys 197: The Salisbury Crag is dangerous but, so ah’m sortay no daein it again.