OK, I heard back from refunds, but in the form of the geeky Portuguese version of the conditions attached to the ticket. Helpful.
The scary thing is the ticket is broken down into its four component flights, MAN LIS, LIS SFO, SFO LIS and LIS MAN. Under each component it lists a cancellation fee of EUR115. So that'll be EUR460 penalty?
I phoned the help team again, this time selecting the Portuguese option in the hope of greater clarity.
They assure me that the cancellation penalty applies to the trip in each direction, rather than to each flight. Say the per flight reference in the conditions is "just the way it is written".
The agent puts forward the option of cancelling the return journey for just EUR115, and receiving a refund of half the round-trip ticket i've paid for This interests me, but she goes on to advise me I should do the cancellation only after I've completed the outward journey to SFO, "to avoid complications". I lose interest.
All very TAP. And though the option of turning the ticket into cheap one-way is attractive, I have about as much confidence in TAP as I do in our future prime minister.
I've had a long history with TAP. They holed our relationship below the waterline on a trip to Sao Tome last year; after the lounge access debacle, the withdrawal of hotel accommodation in Lisbon when demanded by their schedule and this latest farce, I've stopping baling the water out.