I imagine Tim, being British, is referring to the rash of hostile corporate takeovers in the 1950s and 1960s in the UK. A useful summary can be found here (PDF link). Charles Clore led the way in 1953, and then in 1958 the Bank of England seemed to encourage the British Aluminium takeover, which changed attitudes completely when upstart merchant bank SG Warburg triumphed over the old school:
According to one historian, “the humiliation of the City Consortium changed City attitudes to takeovers overnight and henceforth financial advisers added hostile bids to their repertoire of merger and acquisition techniques.”
The 1960s continued to be a time of pretty free-wheeling takeovers in the City of London until the (voluntary, not regulatory) establishment of the Takeover Panel in 1968.