The younger brother of Saudi King Salman, Ahmed bin Abdulaziz Al Saud, has arrived home from London to tackle the "toxic" crown prince Mohammed bin Salman, under the security guarantees of the U.S. and the U.K., the Middle East Eye reported late Tuesday.

Al Saud, who is in his seventies now, is among the Al Saud family members who have "realized that MBS has become toxic," the website added, citing a Saudi source close to the prince.

An open critic of the controversial crown prince, the royal is also a former interior minister.

"The prince wants to play a role to make these changes, which means either he himself will play a major role in any new arrangement or to help to choose an alternative to MBS," the MEE also quoted the source as saying.

Although a dissident, his confidence to go back home without the fear of getting arrested or attacked is because of his senior status, the website explained, also adding that U.S. and U.K. officials assured him "they would not let him be harmed" and "encouraged him to play the role of usurper."

As he is among the sons of King Abdulaziz, the founder of the Saudi state, he was not even touched during last year's purge by the crown prince, who could not dare to make an enemy of the children of the founding father during the cleanup.