The Australian naval ship HMAS Adelaide was expected to set sail on Friday carrying British aid, including 90 family-sized tents, eight community tents, and six wheelbarrows requested by the Tongan government.

At the same time, the Royal Navy's offshore patrol vessel HMS Spey will sail from Tahiti to Tonga carrying water and medical supplies.

HMS Spey is expected to arrive next week and the ship's commanding officer Commander Mike Proudman said: "I'm proud that the Royal Navy can play its part in the efforts to respond to the devastating volcanic eruption and tsunami in Tonga."

The UK has also offered to fund the deployment of crisis experts through the United Nations.

Foreign Secretary Liz Truss said: "Our thoughts are with those caught up in the appalling devastation and loss of life caused by the tsunami in Tonga."

What happened in Tonga?

The Hunga Tonga-Hunga Haʻapai underwater volcano erupted on 13 January and 15 January.

The eruption was so powerful that it could be heard from as far away as Fiji, New Zealand, and Australia.

It also caused a tsunami.

Officials from the UN's humanitarian arm estimated that roughly 84,000 people - or more than 80% of Tonga's population - were affected by the eruption.

At least three people were killed - including one Briton, homes have been destroyed on several islands, and the country has been left with a polluted water supply.

The disaster also knocked out communications for the nation of about 105,000 people, cutting it off from the rest of the world.

Humanitarian aid and a message from the Queen

The first planes carrying foreign aid arrived in Tonga on 20 January, five days after the tsunami and once a blanket of ash could be cleared from the airport runway.

They were a Royal New Zealand Air Force C-130 Hercules and an Australian Globemaster aircraft.

Between them, they carried water containers, desalination equipment, shelters, kitchens, a sweeper to remove ash, generators, hygiene kits, and communications equipment.

Great care was needed, as Tonga is one of the few countries to have avoided any community transmission of COVID-19 so far in the pandemic.

Aid from Japan is also on the way.

Some telephone connections have been restored, but it could take another month for full services to resume.

The Queen sent a message of condolence to His Majesty Tupou VI, the King of Tonga, on Thursday.

"I am shocked and saddened by the impact of the volcanic eruption and tsunami in Tonga," she said.

"My thoughts and prayers are with the people of Tonga, as you work together to recover from the damage caused.

"It must be incredibly difficult for those who are unable to contact friends and family while communications are disrupted, and I hope that they will soon be restored."