Never tell the cashier your email no matter what assurances they give you

Cashiers are not just after your money at the till, they often want your email ­address too.

It can seem like an innocent request – they want to ­send you a receipt. But it may lead to a load of unwanted ­marketing ­messages, at odds with data ­protection laws.

Since the launch of the new laws last year, which most people know as GDPR or the Data Protection Act, I have been swamped with letters and emails on the subject.

The constant theme is retailers breaching your data rights. And I experienced it myself this week.

On Monday I bought a ­computer from one of the High Street ­electrical retailers.

What happened next

The first email was OK, but the second... (Getty)

At the till I was asked for my details, including my email address. I quizzed them on why and was told, sure enough, it was so they could email me a receipt.

I then asked for confirmation that my details would not be used for marketing purposes and was assured they would not be.

Within two hours the email ­receipt arrived in my inbox as promised. I was fairly impressed.

But the following day I received a further email which read: “Thank you for buying cloud ­storage” from the retailer.

It then went on to ask me to press a link to activate the account.

The problem was I had not ­purchased any cloud storage. And I discovered this was actually an offer to accept a 14-day trial of cloud storage, which was being provided by a third party.

How to keep your data safe and your rights to make companies delete it 

What they did wrong

This was, therefore, a marketing email. It was a blatant breach of data protection laws. I had not given permission for my email ­to be used for marketing purposes.

I had not agreed for my personal data to be passed on to a third party, so this was another breach. It got worse.

On Thursday I got another email about the cloud storage proposition, despite the fact I had selected the unsubscribe link. So this was a third breach.

I have reported this to the Information Commissioners Office and will see what they say.

Next time you are asked for your email address at the till you may want to politely decline.