Mohammed bin Salman, the divisive crown prince of Saudi Arabiainfo-icon, arrived in London on Wednesday for a three-day state visit. The 32-year-old was greeted at the airport by Foreign Secretary Boris Johnson and had lunch with Queen Elizabeth II, a rare honor for a man not yet head of state.

Later, he will dine with Prince Charles and Prince William - two British royals who are, like him, next in line to the throne, although they hold a fraction of his political power.

But the pomp and the red carpet notwithstanding, Mohammed's visit already has turned into a bitter PR battle between those who support the moves he is making for Saudi Arabia and those who call him a "warinfo-icon criminal."

In some cases, the battle veered into absurd territory, such as when pro-Saudi advertisements were placed next to online articles criticizing the crown prince.

Although Mohammed has pushed through some liberal policies at home - including his dramatic decision to allow women to drive - and he is viewed as a key economic ally for a post-Brexit Britain, his foreign policyinfo-icon is controversial in London.

Notably, the crown prince is the architect of a Saudi-led intervention against Iraninfo-icon-allied rebels in Yemeninfo-icon. Critics say Saudi Arabia's indiscriminate use of force in that conflictinfo-icon has had disastrous consequences for Yemeni civilians, exacerbating what may be the worst humanitarian disaster on Earthinfo-icon.

According to U.N. estimates from last year, more than 10,000 people have been killed in Yemen since 2015. More than 3 million people have been displaced, the United Nationsinfo-icon estimated, and 80 percent of the population is in need of humanitarian aid.

 Awkwardly for Johnson and Prime Minister Theresa May, Britain is a key military supplier of Saudi Arabia. According to one estimate, sales of British weaponsinfo-icon to Saudi Arabia increased almost 500 percent, to 4.6 billion pounds ($6.4 billion), after 2015, when the Saudi intervention in Yemen began. Saudi Arabia is now the top destination for British-manufactured weapons.

A poll commissioned by the Campaign Against Arms Trade and carried out by Populus found that only 6 percent of the British public supported arms sales to Saudi Arabia; 37 percent opposed Mohammed's visit to Britain.

Amid this public mistrust, advertisements praising Mohammed's reforms have been blanketing London - in an apparent bid to woo Britons. The advertisements have appeared on billboards, on taxis, on trucks and in newspapers.

AEI Saudi, the firm behind the advertisements, is a consulting businessinfo-icon that was registered in Riyadh in 2002. In a blog post, the firm's founder highlighted the significant changes he has seen in recent years in Saudi Arabia, such as a new inclusion of Saudi women in public life.

"If there is one individual who has been the driving force behind these changes it is 'MbS', as he is often known," wrote Adam Hosier, the British-born founder of the firm. "He has faced resistance of course, both internally and from powers outside the Kingdom, yet he has not faltered."

But these were not the only advertisements greeting the crown prince. In central London, buses were emblazoned with messages accusing Mohammed of being a "war criminal," while social mediainfo-icon users used hashtags to let the Saudi royal know that he was "not welcome."

Activists from Avaaz, a global activism group, parked a van outside Parliament and had two figures dressed as Mohammed and May drop off child-size body bags. A sign on the van said May should tell the crown prince: "Stop the slaughter, start peace talks!"

Save the Children, a London-based charity, also highlighted the plight of children in Yemen by placing outside Parliament a small statue of a child standing in rubble and staring at the sky.

Meanwhile, the Arab Organization for Human Rightsinfo-icon in UKinfo-icon has scheduled a protest outside Downing Street, due to start at 5 p.m. local time.

It is unclear who is winning the PR battle - other than advertising agencies, of course. The pro-Saudi messages were certainly mocked: Some noted that the advertisements looked better suited to a "sleazy gentlemen's club" and pointed out that online ads praising Mohammed had appeared next to articles about Saudi corruptioninfo-icon.

Many of the billboards welcoming the crown prince appeared along the motorways that connect Heathrow Airport to central London - suggesting that Mohammed may have been the intended audience.

However, the protests outside Parliament seem to have resonated inside Westminster. During the weekly Prime Minister's Question Time on Wednesday afternoon, opposition leader Jeremy Corbyn criticized Saudi Arabia's record on human rights and accused May of "colluding" in suspected war crimes in Yemen.

"The link that we have with Saudi Arabia is historic, it is an important one, and it has saved the lives of potentially hundreds of people in this country," May responded, as opposition lawmakers shouted "shame."

May later said that she would raise the issue of human rights with the crown prince when she met him and that she had spoken with him about humanitarian concerns in Yemen during a visit to Riyadh in December.

The controversy over Saudi Arabia puts May in a tight spot politically. Britain is looking for bigger trading partners as it leaves the European Unioninfo-icon, and broadening its economic relationship with Saudi Arabia would help it do that. The two nations are planning to create a joint Strategic Partnership Council that could lead to Saudi investment of up to 100 billion pounds ($139 billion) in the next 10 years, according to the BBC.

However, the visit is also important for the Saudi crown prince, who is seeking foreign investment as part of Vision 2030, his ambitious plan to reform his country. There are also hopes that the long-awaited public listing of the state oil firm Saudi Aramco might take place on the London Stock Exchange.

Mohammed also is planning to visit the United States, home to the New York Stock Exchange, for an investment-focused visit set to start March 19.