The 32-year-old crown prince is seen by some as a modernising force in Saudi Arabia.
British Prime Minister Theresa May has promised to press Saudi Arabia over its human rights record during the crown prince's three-day visit to the UK.
Mohammed bin Salman's historic first official trip is aimed at strengthening economic ties between the two countries.
But Labour leader Jeremy Corbyn urged the prime minister to use the occasion to condemn human rights abuses.
Protesters are planning to target Saudi officials over Yemen and other human rights issues, and Britain for licensing 4.6 billion pounds of weapons sales to Saudi Arabia since 2015.
May has promised that she will be "raising concerns about human rights with the crown prince when I meet him."