John King was only a small part in Lakers downfall. There was a combination of factors.
Firstly, it was a cartel of several airlines that undercut Freddie not just BA
Secondly Freddie borrowed money in US$ from banks or thru lease deals with the manufacturer. The airlines principle income was in £sterling. During the late 70's-early 80's the value of the £ collapsed against the $, therefore sending his loan repayments thru the roof, and the airline rapidly became insolvent.
Too many bitter people here blaming one man for their personal misfortune. JK was a man doing a job he was employed for, simple as that.