So I've got what I think is an interesting email back from Swiss Customer Relations.
In short, had flights with them which were cancelled. Started off the charge-back route, which got denied due to the standard immigration bulls*t they've been spouting to everyone.
I wrote them a "Letter before Action" enclosing their CoC and 261/2004, giving them seven days to pay or I'll take out action in the English Small Claims Court. That did the trick with an apologetic email from customer relations and the money now back on the Amex. I pressed them on why they declined the chargeback when they did acknowledge in writing that I was fully entitled to the refund.
They came back with the following:
Originally Posted by Swiss
I regret that we failed to meet the standards we committed ourselves to with regards to refund processing times and I understand your frustration in light of the unsuccessful refund request and chargeback attempt. We deem it important to carefully check each refund request. For this reason, all chargebacks have been disputed as the relevant department confronted with these is neither trained to do the necessary checks nor has the capacity to do so. While we received chargeback requests by passengers with a clear entitlement to a refund, there are also other cases to be considered, such as cancellations by passengers who felt it was unsafe to fly or who were unable to fly due to immigration restrictions and also requested refunds. In order to follow a transparent and fair refund process, chargebacks have thus not been agreed to with regard to Coronavirus irregularities, but referred back to our Refunds Department.
I find this fascinating - they're simply disputing all chargebacks regardless. If I were Amex (or indeed MC/Visa), surely I'd be interested in a merchant blatantly abusing the process to their own ends?