Crown Prince of Saudi Arabia Mohammed bin Salman’s final day of visit to UK will turn to defense and security.

Saudi prince will meet British defense minister Gavin Williamson on Friday, touching on the most controversial aspect of his trip: arms sales.

Friday’s meeting is expected to include talks on the sale of up to 48 Typhoon fighter jets made by British firm BAE Systems to Saudi Arabia, which is a multi-billion pound deal.

British Prime Minister Theresa May defended the two countries' defense ties on Wednesday, claiming all weapons sales to Riyadh were strictly regulated.

Bin Salman's arrival in London was marked by a wave of protests against Saudi Arabia's human rights violations and its deadly war on Yemen.

Saudi Arabia and its allies launched the war on Yemen in March 2015 to reinstall its former Riyadh-allied government.

The Saudi-led military aggression has so far killed over 13,600 Yemenis.

The war is being led by bin Salman, also Saudi Arabia’s defense minister, with the help of the US and the UK.

The UK has, so far, sold more than six billion pounds of arms to Saudi Arabia.