May later met Prince Mohammed at her Downing Street office, extending a warm diplomatic welcome to the conservative kingdom's heir apparent and agreeing a 65 billion pound ($90.29 billion) trade and investment target.
There were crowds of protesters and supporters of the royal visit on Downing Street, being separated by police.
An Egyptian newspaper has quoted bin Salman as describing Iran and Turkey as part of a "triangle of evil" in region, during a visit to Cairo on his first foreign trip since becoming heir to the Saudi Kingdom a year ago.
"Providing access to opportunities for people to reach their full potential is core to our mission and Ford's goal of becoming the world's most trusted mobility company", said Jim Vella, President, Ford Fund. The Save the Children charity protested the visit by installing a statue of a child near parliament "to draw attention to the violence that is being fuelled, in part, by British-made bombs".
Saudi Arabia's crown prince has vowed to promote religious freedom in a private meeting with the archbishop of Canterbury in Lambeth Palace today. "Stop arms sale to Saudi Arabia" and "Bin Salman is a War Criminal". However, only 6% of British public support it. May said their close security cooperation had saved British lives.
The Saudi foreign minister, Adel Al Jubeir, has responded to the massive protests, claiming they are based on a "misunderstanding" of his country's military aggression against Yemen, the poorest Arab country.
The Prince of Wales with Saudi Crown Prince Mohammed bin Salman and the Duke of Cambridge before they had dinner at Clarence House London
May responded that her relationship with Prince Mohammed had already helped alleviate the humanitarian crisis by convincing him to ease Saudi blockades of ports in Yemen during a meeting in December.
Following the talks, a Downing Street spokeswoman said May "welcomed recent reforms in Saudi Arabia, including on women" and had raised Britain's "deep concerns" at the humanitarian situation in Yemen.
"The archbishop voiced his distress at the humanitarian crisis in Yemen, and asked that all that is possible be done to alleviate the suffering of civilian populations and to seek an end to the conflict", the statement said.
He added that the Saudi-UK Strategic Partnership brings together eight joint programs.
For those who have criticized Saudi Arabia as a country that moves at a snail's pace, the pace of change has literally taken everyone by surprise and make the same people now say slow down.
Later this month Prince Mohammed visits the United States, which also wants the lucrative listing, although sources said both countries might miss out.
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He is also believes that Prince Charles will never wear the crown and the Duke and Duchess of Cambridge will have a fourth child. But on the small screen she's been a key part of helping to make Suits a big success and the show gave her her big break.