Merkur Island Shipping Corp. v Laughton [1983]

C owned ship docked in
Liverpool, which was under charter to B and sub-charter to NL.
NL had contract with tug
owners to take ship out.
Trade union, wishing to
pressurise C, persuaded tug crews to refuse to move ship.
House of Lords held it was unlawful interference
in contract between B and C, even though inducement many steps removed from contract.
However, more indirect the interference,
the more difficult it was to establish that A intended to interfere and that interference
was necessary consequence of A’s act.