Cariadagain The banks have many checks and balances in play that are automatic. One of these is that their computers contain a model of your normal expenditure pattern based on your spending and being adjusted all the time - for example, most of what is charged to your card is mainly food shopping, fuel and other things, usually within 50 miles of home.
These are simple electronic based systems based on the information within the system. If you suddenly change your spending pattern or spend a lot elsewhere they are instantly on the alert, in case your card has been cloned or otherwise misused by others.
In the last six months w have moved home and started to renovate an old house. Suddenly we are ordering home furnishings, DIY materials, more meals out, in places we have never visited before. For the first 2 months both of us had real problems with our credit card. Mine was frozen at one point.
However, now all our financial documents have our new home address on them and the various machines behind these cards have adjusted to our new spending pattern , I know that if were to go to Bedford and, for example, spend £500 at Dunelm, my cardd would now see that as part of my new spending pattern at my new address, where as three months ago, an alert would have been raised.