Vin Murria held talks with M&C Saatchi about joining as a non-executive director but turned down the approach, before deciding to buy a 13.25% stake to become the largest shareholder.
It is thought that Murria, a serial technology entrepreneur, met some of M&C Saatchi's top team to discuss joining the board around the beginning of 2020, following an exodus of directors in December 2019 over an accounting scandal.
The revelation casts fresh light on Murria's decision to spend an estimated £6m to buy her stake on 30 April.
Rather than simply joining the board, she has positioned herself to play a potentially active role in the future of the agency group.
Murria and M&C Saatchi offered no comment when contacted by Campaign.
M&C Saatchi was rocked by scandal last year, when the group had to make £11.6m in accounting adjustments.
Lord Saatchi, one of the co-founders, and all three of the non-executive directors quit in December.
Three other co-founders – chief executive David Kershaw, executive chairman Jeremy Sinclair and executive director Bill Muirhead – had to rebuild the board and subsequently recruited four NEDs.
Murria has a low profile in advertising circles, but was a non-executive director at Chime Communications, a rival to M&C Saatchi, from 2013 to 2015, when it was on the stock market and WPP was a minority shareholder.
She holds a number of other non-executive directorships and added another NED role at Bunzl in April.
Murria, who is 57, founded Advance, a computer software group, in 2008 and made a reported £100m when she sold it in 2015.
Kershaw, who is 66, and Sinclair and Muirhead, both 73, each have stakes of 3.98% in M&C Saatchi, giving them a combined shareholding of almost 12%.
The trio founded M&C Saatchi in 1995 with Maurice and Charles Saatchi, after they all previously worked at Saatchi & Saatchi.
M&C Saatchi's share price has plunged from 330p in August 2019, when the accounting problems first emerged. The stock price closed at 39.5p on 30 April, the day when Murria bought her stake.
News of her investment sent the stock up to about 65p by the end of last week, making her stake worth close to £10m and valuing the group at about £75m.
Other leading shareholders include Invesco Perpetual with 12.3%, Octopus Investments with 9.3% and Paradice Investment Management with 8.4%.