The President of Mexico is to begin his state visit to the UK as the Queen prepares to greet him with a ceremonial welcome and stage a banquet in his honour.
Enrique Pena Nieto and his wife Angelica Rivera with meet the monarch and the Duke of Edinburgh amid pomp and pageantry on Horse Guards Parade in central London, before joining them for a grand carriage procession along The Mall to Buckingham Palace.
Human rights campaigners are using the president's three day stay to highlight what Amnesty International UK has described as "out of control" torture in Mexico.
The embattled president has faced growing pressure and public unrest amid anger over the handling of the abduction and apparent murder of 43 trainee teachers by corrupt police in league with gang members.
The students' disappearance in Ayotzinapa in September sparked weeks of protests across Mexico against corruption and violence.
Amnesty has reported a six-fold increase in the number of reported torture cases in Mexico in the past decade.
The upsurge has coincided with the country's nine-year-long "war on drugs", which has also seen over 100,000 killings and over 22,000 disappearances, the human rights group said.
Mr Pena Nieto came under fire at the Oscars, when Mexican film director Alejandro Gonzalez Inarritu used his victory speech for Birdman to declare: "I pray that we can build the government that we deserve."
The president and his wife - a glamorous ex-telenovela actress - will be met by the Prince of Wales and the Duchess of Cornwall at the Intercontinental London Park Lane Hotel before travelling with them to the parade ground.
This evening, some 170 guests will gather in the Buckingham Palace ballroom for a lavish state banquet, where both the Queen and the president will give speeches.
Mr Pena Nieto and the First Lady, who are staying with the Queen at the Palace, are facing the fall out from what became known as the "White House" conflict of interest scandal.
Ms Rivera was in the process of paying for a lavish £4.4 million property when it was revealed that it was owned by a company which has benefited substantially from her husband's presidency.
She posted a video statement on her website to explain the situation, outlining her personal wealth from her acting career and announcing her decision to sell her stake in the mansion to defend "my integrity, that of my children, and my husband".
She was previously more famous than her husband and starred in the hit Mexican soap opera Distilling Love. She is known as the La Gaviota - the seagull - the name of the girl she played in the show.
Mr Pena Nieto, 48, came to power in 2012, representing the Institutional Revolutionary Party (PRI) which ruled Mexico for 71 years until 2000.
He vowed to focus on curbing violence and insisted he would not make pacts with organised crime.
Some refer to him by the nickname Bombon - sweetie - which female admirers would scream at him during election rallies. A former governor of the state of Mexico, he was frequently dubbed Mexico's most handsome politician.
Mr Pena Nieto will hold talks with the Prime Minister on Wednesday, with Amnesty urging David Cameron to tackle the country over its record on torture.
Tom Davies, Amnesty International UK's Stop Torture campaign manager, said: "While President Pena Nieto is getting the red-carpet treatment, his police and security services have serious blood on their hands.
"With public officials complicit in drug cartel crimes as well as thousands of torture cases of its own, President Pena Nieto needs to radically overhaul his country's woeful response to this crisis."
The campaign group Yo Soy 132 Londres, who sent a letter to the Queen demanding an independent investigation into the students' case, will today stage a protest outside Downing Street under the banner #EPNnotWelcome.
The incoming state visit takes place just four months after Charles and Camilla carried out an official tour to Mexico.
The country has the second-largest economy in Latin America and is a major oil producer and exporter. The president will travel to Aberdeen on Thursday to attend a reception with representatives from the oil and gas sector.