Demonstrators gathered amid opposition to the visit over Saudi Arabia's alleged human rights abuses. He had lunch with Queen Elizabeth II at Buckingham Palace on Wednesday and is scheduled to dine later with Prince Charles and Prince William.
However, his arrival drew protests on the streets of London over the brutal Yemen conflict.
The prime minister praised Saudi's "ambitious reform program" and offered the U.K.'s support "to progress and intensify these reforms, particularly on women's rights, and on universal human rights", the Downing Street statement said.
New analysis of executions in Saudi Arabia by Reprieve shows that since Mohammed bin Salman was appointed as Crown Prince in June 2017, the rate of executions in the Kingdom has doubled.
But Prince Salman's three-day visit is expected to be overshadowed by protests throughout.
Britain is looking for trading partners at a time when it comes out of the European Union and Saudi Arabia has to convince skeptical investors about the success of its internal reforms. The war has been made possible in large part by the regular sale of weapons to Saudi Arabia from the United Kingdom and the United States.
"We're here to challenge the link between the British government and the Saudi regime, which has created the worst humanitarian disaster in the world today in Yemen", Bell said at the scene. "Their involvement in Yemen came at the request of the legitimate government of the Yemen, it is backed by the UN Security Council and as such we support it".
The UK has licensed more than $6.4bn in arms to Saudi Arabia since the start of the war in Yemen in 2015, including advanced jets and munitions.
South African Triathlete Attacked with Chainsaw Tried Hacking His Legs Off
Jackson said Gwala told him that the attackers sawed into his right calf (with a boring blade), damaging muscle, nerves and bone. Gwala has represented South Africa at worldwide competitions in Chicago in 2015 and in the Netherlands a year ago .
Despite the demonstrations, however, British officials said they hoped to capitalise on the Saudi economy's opening up.
"We do need trade, we do need good relations with countries, but that is very different from supporting a regime that breaks global law, again and again and again", he stressed.
Dr. Mohamed Ramady is an energy economist and geo political expert on the GCC and former Professor at King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia and co author of "OPEC in a Post Shale world - where to next?'".
The prime minister intends to use the private dinner at Chequers, a 16th-century manor house 40 miles (60 kilometers) northwest of London, to further press her concerns over the humanitarian crisis in Yemen, her spokesman said.
It has laid the cornerstone for a long term mutual beneficial relationship Britain and sets out an ambition to build 65 billion pounds ($90.29 billion) of trade and investment ties in coming years.
The trip is the Crown Prince's first foreign tour as heir to the Saudi throne and is seen as his chance to project the kingdom as a "reforming youthful society determined to take up its status as a major G20 economic power". If he can not succeed in his mission to secure Saudi's border and its economic future, he may just find the line of succession changes.
London taxis display advertising graphics welcoming Prince Mohammed and electronic billboards promote the visit.
Shadow Foreign Secretary Emily Thornberry penned an op-ed in The Guardian slamming the government, saying: "Britain's red carpet for the Saudi ruler is shameless".