Manager Moyes welcomed Dawson, who could make his transfer to London Stadium permanent at the end of the 2020/21 season, and says his professionalism and leadership qualities will be welcome additions to the squad.
Now, most West Ham fans will be desperate for David Sullivan to get this one over the line.
Apparently the 25-year-old has fallen out with the Championship club's hierarchy over broken promises.
According to an earlier report by The Sun, long-term admirers Crystal Palace had been waiting "weeks" for the opportune moment to formalise their interest, with the Eagles keen to avoid a bidding war with their Premier League rivals for Benrahma's signature.
Benrahma was allegedly of the belief that he was owed a loyalty by the Bees, that was yet to be paid.
It would be surprising if he stayed at Brentford after falling out with the club hierarchy.
West Ham are now very weak in the left wing department.
Alternatively, Joshua King remains an option and the Hammers have already had a £13m bid turned away by Bournemouth.
The Irons are said to be bringing in the winger as a replacement for Felipe Anderson, who joined FC Porto on loan last week.
Jack Wilshere's wages will also help fund a move after the club reached an agreement to end his contract in east London.
West Ham United are pleased to announce the signing of versatile defender Craig Dawson on a season-long loan from Watford.