It was the British who backed the Saud family initially. Towards the end of the Ottoman empire. They gave the Sauds advisers and military support.
https://en.wikipedia.org/wiki/Ibn_Saud
Excerpt: "After World War I, he received further support from the British, including a glut of surplus munitions. He launched his campaign against the Al Rashidi in 1920; by 1922 they had been all but destroyed."
Looks like the Brits love supporting everyone ;)