It is not the end of the owners' involvement, they remain interested and invested throughout the process.
But one of the success stories of the takeover has been the celebrity pair knowing their own limits – and placing trust in the expertise of others.
That very much includes Parkinson who draws up his list of targets, working closely with assistant Steve Parkin and scout Chris Johnson.
The budget from the board meeting gives Parkinson an idea of what he is working with as they move towards the window.
But while the final say on who ends up coming through the doors at Stok Cae Ras is always with the manager, support and scrutiny comes in the form of a transfer committee.
Parkinson is joined by Williamson, as well as directors Humphrey Ker and Shaun Harvey.
Then there is former FA technical director Les Reed. The one-time Charlton Athletic manager was a key decision-maker at Southampton as they went from League One to the Premier League, a period where the club won praise for the recruitment of players such as Virgil van Dijk and Sadio Mane.
He has been an advisor and consultant from the early days of Reynolds and Mac's time, even helping identify Parkinson as their choice for manager.
The five together make sure there is a collective responsibility on the approach and, crucially, if the moves are right for the club.
Williamson has described it as a "stress test" of the process, with meetings both virtually and in person as the window demands.