South Korea's presidential scandal
In 2016, South Korea saw the start of a massive corruption scandal involving its political and business elite that brought down its first female president Park Geun-hye.
The scandal, which continues to ripple through South Korean society, has generated huge protests.
It has centred on Ms Park's relationship with an old friend, Choi Soon-sil, and has brought to the surface allegations of cult activities, influence-peddling and leaks of classified information.
What is the relationship at the heart of the scandal?
In 1974, Park Geun-hye's mother was killed by a North Korean assassin.
Ms Park, then aged 22, became a stand-in first lady for her widowed father, then-military leader Park Chung-hee.
She got to know Choi Tae-min, a pseudo-Christian cult leader dubbed "the Korean Rasputin".
He became a close family friend and Ms Park's mentor, while also amassing considerable wealth and power.
Ms Park's father was assassinated in 1979. By this point she was firm friends with Mr Choi's daughter, Choi Soon-sil, who later became her adviser when Ms Park became president.
Their critics believe Choi perpetuated her father's habits, and some media reports suggested that Ms Park held shamanist rituals at the presidential compound under Choi's influence, which Ms Park denied.
Why has the friendship become problematic?
In June 2017, Choi was jailed for three years for corruption, after she was found guilty of using her position to solicit favours for her daughter.
She still faces trial for various offences, including abuse of authority, coercion, attempted coercion and attempted fraud.
One of the main accusations levelled against Choi was that she used her presidential connections to pressure conglomerates - including electronics giant Samsung - for millions of dollars in donations to two non-profit foundations she controlled.
Ms Park meanwhile has been accused of colluding with Choi.
Ms Park was officially ousted in March 2017, following parliament's decision to impeach her in December. She was the country's first democratically-elected president to be forced from office.
After losing her presidential immunity, she was charged with bribery, abusing state power and leaking state secrets, and her trial began in May.
Choi is also accused of having received large numbers of confidential government documents from Ms Park, via an aide.
Both women have since denied wrongdoing. They had earlier apologised, but it was unclear exactly what they were apologising for.
Choi said she had committed an "unpardonable crime", though her lawyer said this was not a legal admission of guilt.
Ms Park admitted she had committed lapses, and apologised to the public for causing "national concern".
So how is Samsung involved?
The firm is one of eight that has admitted making payments to the foundation, but denies it did so in return for any favours.
In August 2017, Samsung's de facto head, Lee Jae-yong, was jailed for five years for bribery and embezzlement.
Lee was convicted over payments of 43bn won ($36.4m; £30.3m) made to Choi's foundations, as well as for giving a horse and several million dollars to assist the equestrian career of Choi's daughter.
Prosecutors had accused Lee of approving these payments and gifts in order to win government support for a major restructuring of Samsung.
The 2015 merger of two Samsung units, which paved the way for Lee to become the eventual head of South Korea's largest conglomerate, sparked controversy at that time.
While Lee did not dispute that the payments were made, he maintained during his trial that he was not involved in the decisions and denied that he sought government favours.
Lee was also found guilty of hiding assets overseas, concealing criminal proceeds, and perjury. He is appealing against his conviction.
Is anyone else involved?
A host of other players have either been implicated, investigated or jailed in connection with the wide-reaching scandal.
These include Samsung executives, various figures in the entertainment world, a former minister, presidential aides, university officials and former associates.
One of them is Choi's daughter, Chung Yoo-ra, a former national equestrian and recipient of Samsung's gift horse.
Choi was convicted for influencing officials at Ms Chung's university to admit her daughter and give her grades for papers or exams she never took.
Prosecutors say Ms Chung was involved in or had knowledge of several of her mother's crimes, but she has denied it.
She was extradited to South Korea from Denmark in early 2017, but has not been detained.
How has the scandal affected South Korean society?
Since it began the whole affair has prompted numerous mass protests in South Korea, many of which called for Ms Park to step down.
It has fuelled discontent against the government, the political elite and family-run conglomerates which dominate South Korea's economy.
Though Choi and Lee have been convicted, many are still waiting to see what happens in Ms Park's court case which is due to be wrapped up in the coming months.
For many South Koreans, the former president who has been at the centre of one of the country's biggest scandals still has a lot to answer for.