The launch of Android Pay gives mobile payment capability to millions of Android smartphone users for the first time.

:: How does Android Pay work?

Using sensor technology built into most Android smartphones called near-field communication (NFC), a phone can be tapped against any contactless payment point - whether it be a card reader in shops such as Boots and Marks & Spencer or a tap-in point on the London transport network - to complete a transaction linked to your bank account.

A free Android Pay app connects and sets up the system, which can be linked to any account using Visa or MasterCard. The system also works within apps as an alternative, quicker form of payment as well as in stores.

:: Which smartphones are compatible?

Any Android smartphone running at least version 4.4 of the mobile operating system and with NFC compatibility can use Android Pay. This means almost every Android device from the likes of Samsung, HTC, Sony, Huawei and others from the past two years should be compatible.

:: Have all the banks signed up?

The majority of UK banks are signed up to Android Pay at launch. Bank of Scotland, First Direct, Halifax, HSBC, Lloyds Bank, M&S Bank, MBNA and Nationwide Building Society have been confirmed as partners by Google, with more banks due to the added, according to the technology giant.

:: Is it secure?

Transactions with Android Pay are protected by a process known as "tokenisation". This means that rather than sharing account details with a vendor each time a transaction is made, special digital tokens are generated and used. Payment and account details are kept secure and encrypted within the device.

:: Do you need to open the app each time you wish to use Android Pay?

No. You can just tap your device against a payment point for transactions under £30. For those over £30 you will need to confirm the payment using a security method like that used to unlock your phone - either a pin, fingerprint or drawn pattern.

:: Where can you use Android Pay?

Anywhere that accepts contactless payment will be compatible with Android Pay, including the likes of Boots, Costa Coffee and Waitrose, as well as across the London transport network thanks to a link with Transport for London (TfL).