More than 100 relatives and friends of British victims of the Bali bombings will gather in London on Friday to mark the 10th anniversary of the terror attacks.
A closed ceremony will be held in the capital for those who lost loved ones in the deadliest attack on Indonesian soil.
A total of 202 people, including 28 Britons, were killed on October 12, 2002 when the al Qaida-linked Jemaah Islamiyah group launched terror attacks on two Bali nightspots packed with tourists.
Various members of Jemaah Islamiyah were convicted in relation to the bombings and three were executed by firing squad in November 2008.
Flowers are laid at the pool of remembrance during a ceremony in Bali
But relatives claim another terrorist associated with the attack - Riduan Isamuddin, known as Hambali - is being held in Guantanamo Bay and are calling for him to stand trial.
The 10th anniversary is being marked in Bali by hundreds of relatives and friends of the victims, but authorities have raised the country's security alert to its highest level after receiving intelligence of a threat to the ceremony.
The Foreign Office is holding a closed ceremony on Friday at the memorial erected in memory of the victims of the bombings which is near St James's Park.
More than 100 family members and friends will attend, along with diplomats from other countries that lost people in the bombings.
Australian Prime Minister Julia Gillard attended a memorial for those killed in the bombings in Indonesia
Foreign Office minister Hugo Swire will make a short speech, and there will be a wreath-laying ceremony as well as a two-minute silence.
Relatives of the 28 British victims have also organised a service at St Paul's Church in Covent Garden.
They have said they want to see a final push to make sure those responsible are held to account.
Susanna Miller, whose brother Dan, 31, died in the attacks, while his wife Polly was badly burned, called for open justice for Hambali, claiming his nine-year detention is an "open travesty of human rights".
A remembrance pool has been created in memory of the 202 who were killed
"We find ourselves in this slightly curious position of fighting for the rights of one of the people responsible for the deaths of our relatives," said Ms Miller.
The 45-year-old, who lives in north London, visited the Foreign Office last week to discuss the issue and a spokesman confirmed it is being looked into.
Ms Miller said many relatives have not travelled to Bali for the anniversary because of security concerns.
And though 10 years is significant, the tragedy remains fresh.
The service in Bali will be followed by another in London
"Time, in many ways, stops still, and you just have to learn to live a different life.
"The more time passes, the more you realise what they have lost and the more family events they miss. In a way it gets sadder, in a way you miss them more on their birthdays, anniversaries, family events."
She said there is a "sense of community" among victims' families.
"But I think most people would say it has split their lives in half - pre-Bali and post-Bali," she added.
"I think all you can do is live a new life, because you can never change what that bomb has done to us and continues to do.
"It's like having an elephant in the room, you just have to learn to live a different life, because it will never be the same, and, frankly, if you are human, it shouldn't be."