It was a decision that started him on a road to being an asset management chief executive, where he has spent the past 15 years, the last five of those at Polar Capital, trying to manage boutique firms at a time when fees have been falling and the share of client assets moving to passive products is constantly rising.
That call was an offer to become chief executive at JO Hambro Capital Management, a fund management business with a strong presence in private equity and property, but a desire to launch mutual funds in the standard asset classes.
But the looming global financial crisis in 2007 made it a tough time to try to expand an asset management firm.
We think performance leads to inflows, so focus on that.
He says: “I had been working very happily at Fleming Family & Partners, a firm which had started as a family office and which became a multi-family office investment firm.
"When Northern Rock collapsed in 2007 I thought a crisis was coming. And the Fleming family said to me: ‘It’s time to batten down the hatches [and prepare the firm for the crisis],' but the thing with me is, I am better at building businesses than maintaining them. So battening down the hatches wouldn’t really suit me.
"With the global crisis coming, I thought I would leave Flemings and take a year off to go sailing until the crisis passed, and then buy a share in a business and try to build it up.”
The phone call was from Christopher Mills, one of the two co-founders of JO Hambro Capital Management, and part of the offer was that Rochussen could acquire a stake in the business.
His role then, similar to his current role at Polar Capital, was heavily focused on poaching and hiring fund managers from other firms to develop JO Hambro's product range.
Rochussen says this approach was particularly effective then because “the crisis meant there were lots of talented managers in quite distressed businesses that we could hire”.
That he would become a career chief executive is probably not a surprise to the very focused Rochussen, but his involvement in asset management was an accident.
Rochussen trained as an accountant in South Africa, running his own practice advising mostly small businesses, and then became chief financial officer at an electronics company, where he was also chairman of the pension fund, and so actively involved in choosing fund managers.