A new travel system for visitors to the UK comes into force from Wednesday for citizens of dozens of countries like the US and Australia.

The government says electronic travel authorisation (ETA) will improve the immigration system.

However, it has created problems for dual nationals, who have been scrambling to get a UK passport to follow the new rules.

An ETA is a digital permission to travel to the UK.

From 25 February, most people who have been able to travel to the UK visa-free until now will need an ETA.

The new rules apply to people from 85 different countries.

Once approved, your ETA will allow you to stay in the UK for up to six months. It will be valid for two years, or until your passport expires, and allows multiple journeys to the UK.

The visit can be for things like tourism, business or short-term study.

It can also be for people who cross the border and travel through the UK as part of a journey, although people transiting through UK airports and who don't need to go through border security will not need an ETA.

Longer trips and visits for work or longer study will require a visa.

People who usually need a visa to travel to the UK will still need a visa to travel to the UK. They will not need to apply for an ETA as well.

British or Irish citizens will not need an ETA or a visa to visit the UK or to travel through it. There are a few other exceptions, such as those with settled status or children travelling from France on a school trip.

The scheme was launched in October 2023 but the government says it was "not strictly enforced to give visitors ample time to adjust to the new requirement".

However, in November, the government said ETAs would be mandatory from 25 February.

The government says ETAs will streamline the immigration system, speed it up and make it more secure.

Getting an ETA costs £16, but the government has said it plans to increase the fee to £20 in the future.

To apply, the government recommends downloading the app from Google Play or the Apple App Store.

You will need to provide contact and passport details, provide a suitable photo, and answer a set of questions.

You must travel using the same passport you used when you applied for the ETA.

The government says most people will get an automatic answer in minutes when using the ETA app, but it recommends people apply at least three working days before travelling.

If a person's ETA application is rejected, the government says they will be told the reason and can apply again.

However, if a person's ETA application is refused, they cannot appeal and instead need to apply for a visa to visit the UK.

When you check into your journey, you may not be able to board without a valid ETA.

Airlines, rail companies and shipping companies have been given tools by the UK government to verify travel permission through automated digital checks with the Home Office.

An ETA is digitally linked to your passport, so you don't need a paper copy at the border. However, the government says you may want to keep a paper copy for your records anyway.

While an ETA gives you permission to visit the UK, it does not give you the right to enter. So you will still need to go through passport control.

You could still be turned away at the border even with a valid ETA if there are other issues at passport control.

Dual nationals - those who are citizens of both the UK and other countries - cannot get an ETA.

To enter the country, they will need to show either a British passport or a new digital version of the certificate of entitlement to attach to their second nationality passport.

Without one of them, they could face being denied the right to travel back to the UK.

Neither British passports nor certificates of entitlement are automatically issued to people who obtain citizenship, which means some dual nationals have never applied for them, even if they have lived in the UK for decades.

Both documents take several weeks to obtain, and there are costs too. A British passport costs about £100 for an adult, while the certificate of entitlement costs £589.

Previously, dual nationals had been able to leave the UK and return using their non-British passport.

Several British dual nationals have told the BBC of their struggle to get a British passport to meet the new requirements.

Some have been outside the country since the rule change has been announced and say they haven't had enough time to adjust to the changes.

A Home Office spokesperson previously told the BBC that "public information advising dual nationals to carry the correct documents has been available since October 2024 and a substantive communications campaign about the introduction of ETA has been running since 2023".

If ETA sounds familiar, it's because Canada, the US, and other countries already use the system.

However, the costs vary.