I am aware that the initial LCY-JFK operation, and the A318 acquisition, was "bankrolled" by a well-known international bank based in the London (and who had developed a substantial operation in New York) who committed to a proportion (20% ?) of the overall seats. Presumably that was a fixed duration and came up for reconsideration. Notably said bank is under instruction from the regulators to reduce their exposure to international trading, and the Chief Executive has indeed changed to one less minded to do so than a prominent predecessor.
The A318s are seemingly only of residual value now, there have been no secondhand transactions and some have actually been scrapped after just a few years of service. I wonder how BA is accounting for them in their audited books.