One was dubbed "The Godfather". The other, "The Enforcer".

Whether those tags ever fit Andrew Chan and Myuran Sukumaran is debatable.

When they were arrested for their parts in the Bali Nine heroin smuggling effort in 2005, they at least looked the part.

Chan, then 21, had a shaved head, gold earrings, tattoos and a smug veneer.

Sukumaran, 24, loomed a head above him - silent and defiant. Surveillance police initially thought he was Chan's bodyguard.

Somewhere in the years after leaving Homebush Boys High School, they drifted away from their supportive working class inner-west families and into Sydney's underbelly.

Chan was the self-confessed black sheep of his Cantonese-speaking family.

But he was known as a hard worker at Eurest, the catering company for the Sydney Cricket Ground.

Sukumaran was a university drop-out, the eldest of three children.

He wanted to be the guy at the nightclubs who bought the drinks, and had fast cars and hot women, but it seemed impossible in his job in a mailroom.

To their church-going families it was a total shock when they learned their sons were arrested in Bali over an attempt to smuggle 8.3kg of heroin, worth around $4 million.

Following an Australian Federal Police tip off, Chan was pulled off a Sydney-bound plane around the same time as four others were caught in Denpasar's departure hall with heroin strapped to their bodies.

The mules - Renae Lawrence, Martin Stephens, Scott Rush and Michael Czugaj - claimed Chan had threatened to kill them and their families if they ran.

"He said he knew everything about us," Rush said at trial.

"He even said he was carrying a gun."

Sukumaran was arrested at the Melasti Hotel in Kuta with around 300g of heroin, along with the other three - Matthew Norman, Si Yi Chen and Tan Duc Thanh Nguyen.

He earned the worst reputation at trial, criticised by the judges for not co-operating and at one stage claiming he had "amnesia".

But the mules had fingered him as being one of the ringleaders who, along with Chan, had taped the drugs to their bodies.

In 2006, Sukumaran and Chan became the first Australians sentenced to death in Indonesia.

The sentence was upheld on appeal and again in a 2011 supreme court review. A bid for a second judicial review was knocked back in February 2015.

President Susilo Bambang Yudhoyono was considered the pair's best chance of winning clemency - friend to Australia as he claimed to be - but he left office without granting their applications.

Incoming President Joko Widodo then signed their death warrants, denying them mercy and putting them on track to the firing squad.

Often played footage of the pair shows them handcuffed together before their sentencing.

Both clad in black pants and white shirts, a menacing Sukumaran barrels through the media pack, lashing out at photographers.

A grimacing Chan is towed along.

By 2010, when the SBS program Dateline visited them in Kerobokan jail, the defiance had vanished.

Chan joked that he was the only "Godfather" who lived at home and drove a 1999 Hyundai S-coupe.

"The Enforcer" was bemused that he'd become a "martial arts expert" in the media when he'd only done three months of training.

By that stage, they admitted their criminality and stupidity.

They were showing they had changed.

Sukumaran was studying for a degree in fine arts and had become an accomplished painter. The studio he lobbied for is used for the therapy and training of other inmates.

Chan's more outgoing personality found a home in the prison chapel and kitchen, where he mentored others and gave cooking classes to boost prisoners' life skills.

Everyone who knew them attested to their transformations.

They are the finest examples of Indonesia's capacity to rehabilitate - a priest and a painter.