The casino mogul famously bankrolled Newt Gingrich's primary efforts, dumping some $21 million into a super-PAC backing the former House Speaker as he vied for the nomination. But after Romney pulled ahead to an insurmountable lead, the pair met privately at Adelson's casino in Las Vegas; since then, the conservative financier has been squarely in Romney's camp.

The fundraiser is just one of many events planned for Romney during his time in Israel. In addition to a summit with Prime Minister Benjamin Netanyahu and resident Shimon Peres, Romney will meet with Palestinian Prime Minister Salam Fayyad and visit the Western Wall.

Romney landed in London on Wednesday, where he is expected to meet with British political figures and attend the opening ceremonies of the Olympic Games.