A British grandmother on death row in Indonesia is writing goodbye letters to her family and believes she could be executed at any time, she wrote in an article on Sunday.

Lindsay Sandiford, 58, said she was expecting to die shortly, after seven foreign drug convicts were executed last week, causing a storm of international protest.

"My execution is imminent and I know I might die at any time now. I could be taken tomorrow from my cell," Sandiford wrote in British newspaper the Mail on Sunday.

"I have started to write goodbye letters to members of my family."

Sandiford, originally from Redcar in northeast England, wrote that she planned to sing the cheery popular song "Magic Moments" when facing the firing squad.

"I won't wear a blindfold. It's not because I'm brave but because I don't want to hide -- I want them to look at me when they shoot me."

She said her greatest sadness is that she may never meet her two-year-old granddaughter, who was born after her arrest.

Sandiford was sentenced to death on the island of Bali in 2013 after she was convicted of trafficking drugs.

Customs officers found cocaine worth an estimated £1.6 million ($2.4 million, 2.2 million euros) hidden in a false bottom in Sandiford's suitcase when she arrived in Bali on a flight from Thailand in 2012.

Sandiford admitted the offences, but says that she agreed to carry the drugs after a drug syndicate threatened to kill her son.

She described Andrew Chan, 31, one of two Australians killed by firing squad on Wednesday for his role in a plan to smuggle heroin, as "one of the heroes of my life".

The two had become close friends in prison, where Chan had spent a decade after being arrested as one of the so-called "Bali Nine" group of smugglers.

The execution of Chan, who became a Christian pastor in prison, and another Australian Myuran Sukumaran, 34, cast a pall over relations between Australia and Indonesia.

A mentally ill Brazilian man and four African men were also executed. A Filipina single mother, Mary Jane Veloso, was granted a last-minute reprieve.

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Sandiford's family have recently launched a fundraising drive to raise money to lodge an appeal at the Indonesian Supreme Court, after the British government refused to fund the legal fight.

If the challenge fails, Sandiford still has the option to appeal for clemency from Indonesian President Joko Widodo.

Mercy pleas of the convicts executed on Wednesday had been rejected.