* Mohammed bin Salman on first official trip as crown prince
* Will meet queen, top officials on three-day London visit
* Anti-war protesters to target Saudis and Brits over Yemen
By William James
LONDON, March 6 (Reuters) - Britain's grand welcome for Saudi Crown Prince Mohammed bin Salman will begin on Wednesday with a lunch with Queen Elizabeth, as the two countries seek to widen longstanding defence ties into a far-reaching partnership.
Both sense an opportunity to broaden their existingrelationship: Britain is looking for trading partners as itexits the European Union, and Saudi Arabia needs to convincesceptical investors about its domestic reforms.
But as Prince Mohammed and Prime Minister Theresa May meet,demonstrators will protest both countries' roles in Yemen wherewar has killed an estimated 10,000 people and where 8.3 millionpeople depend on food aid and 400,000 children havelife-threatening levels of malnutrition.
Inside May's Downing Street offices the two leaders willlaunch a "UK-Saudi Strategic Partnership Council" - aninitiative to encourage Saudi Arabia's economic reforms andfoster more cooperation on issues such as education and culture, as well as defence and security.
"It will usher in a new era of bilateral relations, focusedon a partnership that delivers wide-ranging benefits for both ofus," May's spokesman told reporters.
Britain is vying to land the stock market listing of stateoil firm Saudi Aramco, but no decision is expected this week.
Later this month Prince Mohammed visits the United States,which also wants the lucrative listing, although sources saidboth countries may miss out. officials were privately delighted at the decisionby Prince Mohammed, 32, to choose Britain as the major westerndestination on his first foreign trip since becoming heir to theSaudi throne last year.
The British government is keen to transform its historicdefence relationship into two-way trade and investment, eyeingboth an expanded market in Saudi Arabia for service sectorexports, and attracting Saudi cash to finance domestic projects.
Business deals are possible with British defence group BAESystems BAES.L and European weapons maker MBDA, and initialagreements could be concluded on gas exploration, petrochemicalsand other industries, according to British and Saudi sources.
ROYAL TREATMENT
The three-day visit will include two audiences with theBritish Royal family, a briefing with national securityofficials, and a prestigious visit to the prime minister'scountry residence. intends to use the private dinner at Chequers, a16th-century manor house 40 miles (60 km) northwest of London,to bring up concerns over the humanitarian crisis in Yemen, herspokesman said.
A Saudi-led military coalition is fighting the Houthimovement in Yemen, generating what the United Nation said inJanuary was the world's worst humanitarian crisis. can expect them to discuss Yemen, and the primeminister to raise deep concerns at the humanitarian situation,"May's spokesman said. "She will also reiterate how seriously wetake allegations of violations against internationalhumanitarian law."
Speaking to reporters in London on Monday, Saudi foreignminister Adel al-Jubeir said his country had failed toeffectively communicate the reasons behind its involvement inYemen, but that they had not chosen to start the war.
Protestors are planning to target the Saudi officials overYemen and other human rights issues, and Britain for licensing4.6 billion pounds of weapons sales to Saudi Arabia since 2015.
Buses have spent two days touring London with bannersaccusing Prince Mohammed of war crimes, with more planned forWednesday ahead of the main rally.
"It is vital that people show up to the protest tomorrowoutside Downing Street to make clear that the UK government'scomplicity in the war on Yemen is not supported by the publicand that we demand a peaceful and humane foreign policy," saidLindsey German of the Stop the War Coalition.