Mohammad bin Salman is expected to begin an official visit to the UK on Wednesday, with the ruling Conservative Party and royal family rolling out the red carpet for Saudi Arabia's crown prince as opposition politicians and rights groups call on British Prime Minister Theresa May to use the trip to challenge the kingdom's record on human rights.
Protesters are expected to gather outside Downing Street in London on Wednesday from 17:00 GMT to demonstrate against the visit.
The trip by the crown prince, who is known as MBS, includes a stop at May's countryside residence for talks on Thursday, a lunch with the queen and a dinner with Prince Charles and Prince William.
British Foreign Secretary Boris Johnson had praised the 32-year-old's Vision 2030 national programme, a series of reforms to modernise the Gulf state, writing in a newspaper column on February 28 that the Gulf royal deserved Britain's support.
In the kingdom, Mohammed bin Salman is credited with leading a series of social reforms, such as allowing women to drive and lifting a 35-year ban on cinemas.
However, activists say Saudi Arabia still has a poor human rights record and have warned against interpreting these reforms as heralding new freedoms.
On Tuesday, Jeremy Corbyn, leader of the main opposition Labour Party, joined a chorus of activists, saying that May should tell the crown prince that Britain would no longer supply arms to Riyadh "while the devastating Saudi-led bombing of Yemen continues".
May should also "make clear Britain's strong opposition to widespread human and civil rights abuses in Saudi Arabia", he said.
Caroline Lucas, former leader of the Green Party, tweeted on Tuesday: "Isn't it time we stop giving the red carpet treatment to despots and dictators?"
'Chief architect' of Yemen crisis
According to Downing Street, the meeting will tackle international challenges, such as terrorism, extremism, the conflict and humanitarian crisis in Yemen and other regional issues such as Iraq and Syria.
Since the Saudi-led military intervention started in Yemen in March 2015, the Arab world's poorest country has found itself on the brink of a devastating humanitarian crisis, with at least 10,000 people killed.
British arms companies are some of the biggest suppliers of weapons to Saudi Arabia, and the British government has approved billions of pounds in export licences over the past three years.
Campaigners accuse Mohammad bin Salman of being the "chief architect" of the Yemen war, which has led to what the United Nations describes as the world's worst humanitarian crisis.
"The crown prince has overseen the brutal repression and abuse of Saudi people, as well as terrible atrocities that have been carried out against the people of Yemen," Andrew Smith, head of CAAT, told Al Jazeera.
"Despite his reputation as a liberal and a reformer, he is the figurehead for a regime with one of the worst human rights records in the world."
He accused Britain of failing to hold the Saudi government to account.
"The UK has been totally complicit in these abuses. It has armed and supported the Saudi military for years, with UK fighter jets and bombs playing a central role in the destruction of Yemen.
"The pictures of the crown prince on the steps of Downing Street will be projected around the world, and will be used by the regime to legitimise it on the world stage. Theresa May is handing a major propaganda coup to the dictatorship."
Smith called on the prime minister to halt all arms sales, saying: "For decades now, the UK has prioritised the interests of arms companies over those of Saudi people. For the last three years it has prioritised them over the lives of Yemeni people too. No matter how bad the conflict has got, May and her colleagues have continued pouring weapons into it."