Mr Wanless is a keen Newcastle fan, who has been known to sport football cufflinks in Newcastle colours. He would join three other non-executives on the board, all of whom will be named within the next few weeks.
Sir John Hall, currently the club chairman, would remain as chairman of the football club, which would become a subsidiary of the public company. He would also retain a place on the parent company's board but would not be overall chairman.
NatWest said, however, that Mr Wanless has turned down the job, at least for now. "For a number of reasons, including Mr Wanless's existing business commitments as well as the fact that NatWest Markets is acting as both sponsor and broker to the Newcastle flotation, it was agreed that it would not be appropriate to accept at this time."
But Newcastle sources say that the door remains open to Mr Wanless if he wants to become a director in the future.
If he did, he would join two former employees in senior roles at Newcastle. The day-to-day running of the club is currently in the hands of joint chief executive Mark Corlidge, the former head of NatWest Markets' corporate finance division, while the finance director, Josephine Dixon, worked directly for Mr Wanless as a strategist at NatWest before her appointment to the Newcastle board.