Apple Pay, the contactless payment solution built into the electronics giant's iPhone 6, has launched in the UK.

The system means iPhone users can "tap-and-pay" with their phone for the first time, and many have been doing so for the first time this morning.

The launch marks the first time the software will be available outside the US, and will be on offer to anyone with an iPhone 6 or 6 Plus. It will enable users to tap their phone on contactless payment points to complete transactions - just like a contactless credit card.

There were some complaints from users on social media this morning as it emerged that HSBC and first direct were among banks that were not part of the initial roll-out, meaning some consumers cannot yet take advantage of the service. But Barclays - despite not featuring as a partner previously - confirmed that both it and Barclaycard would be joining Apple Pay "in the future".

The system will also work with the Apple Watch, and the iPhone 5 or newer model it is paired with.

Users of Apple Pay can now hold their phone close to a contactless reader while keeping a finger on the Touch ID fingerprint scanner in order to authorise a payment.

Those with the latest iPad Air 2 or iPad mini 3 will also be able to use Apple Pay within apps to make purchases online.

A host of major UK brands and banks have signed up to support Apple Pay at launch, including Boots, Waitrose and the Post Office, with retailers including Pret a Manger already announcing that the traditional £20 contactless transaction limit will not apply.

While Apple announced a host of partner retailers, anywhere that accepts contactless payment will accept Apple Pay, including the London transport network.

Apple has also said that privacy and security is a key part of Pay, with the iPhone maker explaining that when a credit or debit card is added, the actual card numbers are not stored on the device, or Apple's servers.

Instead, each transaction is completed with a "one-time unique, dynamic security code".

Rival Google is set to launch its own mobile payment solution, Android Pay, later this year, while Barclaycard - as well as joining Apple Pay - has already launched the bPay system, where users can choose between either a wristband, key fob or intelligent sticker for their phone that contains contactless technology and can be linked with any bank account and card.

Contactless payment continues to grow rapidly in popularity, with more than £2 billion spent via the system in 2014, according to the UK Cards Association.