More than 150 relatives and friends of Britons killed in the Boxing Day tsunami last year have returned to mark the first anniversary.
The tsunami killed 149 Britons
A total of 137 will mark the anniversary at sites in Thailand, while another 15 will do so in Sri Lanka.
Many will arrive with the help of the British government, while others will travel there independently.
Meanwhile three Britons caught up in the tsunami in Sri Lanka have spent the last 12 months helping aid projects.
A total of 149 Britons died in the disaster, which is thought to have killed up to 300,000 people across the region.
Those travelling back to the tsunami-affected areas include Tilly Smith, who saved people from a beach in Phuket, Thailand, after recognising some of the signs of an impending tsunami.
Tilly, 11, from Oxshott in Surrey, has been asked to read a poem at a memorial service. She will return with her parents Colin, 47, and Penny, 44.
British tourists dressed as Santa and elves in Unawatuna, Sri Lanka
Richard Galley, 36, from Stoke, and his American wife Kristin Meredith, 33, will spend their honeymoon in Phuket, the same area where they survived the tidal wave a year ago.
The couple married in the summer and now live in Shanghai in China.
Nim Hoy, 41, returned to Khao Lak in Thailand despite losing her diplomat husband John and three children during the disaster to take part in a candlelit vigil.
Mrs Hoy, a classroom assistant from Orpington, Kent, was washed half a mile inland by the force of the waves.
Three Britons teamed up with a German and three Sri Lankans to form Friends of the South, which aims to help local aid projects.
These include housing projects and Swim Lanka, which teaches children not to be scared of the sea.
Founder member Jack Eden has told of his memories of the tsunami last December.
He said: "We had four feet of water throughout the house but no sustainable damage and no injury.
"Living in the Fort, we were protected by the efforts of a Dutchman of the late 1600s who was the engineer responsible for constructing the ramparts.
"Without him - and the ramparts he built - we and about 3,000 others would have died. Without doubt."
Mr Eden said the programme was committed to helping local projects.
He said: "Our intention was to provide financial and professional assistance to existing local charities set up and run by Sri Lankans that, due to their small size, slip through the net of help offered by the government and the big international NGOs," he said.
"We have to be very aware of the structure within a community so as not to interfere with the way things are run and to ensure that, as a result of the aid, we do not unintentionally upset things."