It's an unfortunate fact that older people are often the target of fraudsters. They come in all shapes and sizes, from the builder who offers to repair your roof, to the fake Microsoft engineer who rings to say your computer has been hacked.
The way to protect yourself is not - in my opinion - to think that everyone is going to cheat you but to be aware of the latest ways that con men and women are trying to get hold of the little cash you might have.
The Metropolitan Police maybe responsible for London but they have an excellent website available across the country - and booklet - that keeps you up to date with the latest frauds. Or try Action Fraud (
https://www.actionfraud.police.uk/) that way if you get an unexpected call from a fake BT engineer, or you are offered the investment of a lifetime, you will know how to react. Remember, if it sounds too good to be true, it almost certainly is too good to be true.