People trying to access their account may want to note that the savings group has changed its settings in a bid to improve security. The upgrades include the addition of two-factor authentication (2FA), to make sure that the person logging on is really the account holder.

Scammers can sometimes work out an individual’s NS&I number and even their password, and so the 2FA adds an extra layer of security.

Customers will now receive a one-time passcode sent to their mobile phone as an extra security check.

The code can also be sent by an automated phone call to a landline.

The one-time passcode will be a unique six digit number, and will only work for a short amount of time.

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Lucky Britons win millions of prizes each month through the scheme, with the tax-free winnings ranging from £25 to £1million

The odds of winning are 24,500 to one, for each £1 bond.

Each investment in the bonds must be £25, and they can be purchased online, over the phone or by post.

Money to buy bonds can be paid in from another NS&I account.

There are no penalties for people who need to take out cash from the Government-backed scheme.