On 18/12/2017 10:10, Chris Green wrote:

So extra cards may or may not have the same details as the 'parent'
card, it seems to depend on provider.

It does. We have credit cards which are essentially identical and others
which are completely different.

Accounts with identical cards cancel both if one of them is lost or
stolen, but accounts which have different cards cancel just the one,
leaving the other one still working. This has worked to our advantage
when we've been travelling and one of our cards has been cloned and
cancelled.

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F