The surprise support for the beleaguered fund bosses emerged as Morgan Grenfell battled to contain the damage after the losses run up by Peter Young, the former manager who is being investigated by the Serious Fraud Office.
Geoff Henry, chief executive of the Merchant Navy Officers' Pension Fund, which has invested more than pounds 200m with Morgan Grenfell, said the trustees "would need to consider their position" if Mr Percy's head rolled, or if other senior people who were part of the foundations of the business were sacrificed.
He said: "I'm not saying we would leave. That is the sort of thing that may lead us to leave. You go to an investment manager because of the particular managers that are used rather than the house name."
Mr Henry, who described this as a "gentle warning" to Morgan Grenfell, runs a pounds 2.4bn pension fund.
There were strong suggestions in the City that other institutional clients would review their mandates if Mr Percy was forced to quit merely to prove the parent company, Deutsche Bank, had taken a tough stance against the breakdown in control at the firm, which has cost the group at least pounds 200m.
Paul Haines, investment consultant at Sedgwick Noble Lowndes, said he would expect trustees to review their mandates with Morgan Grenfell if the management changed.
Advice to trustees by professional investment consultants such as Sedgwick Noble Lowndes will be crucial to whether Morgan Grenfell keeps business but also to whether the firm is able to attract new clients.
Morgan Grenfell said it would not know which, if any, senior managers would be forced to step down over the incident until its investigation in to the incident was completed in around three weeks. However, several names are in the firing line and Mr Percy is expected to face pressure from Deutsche Bank to stand down.
Mr Percy is the man behind improving fortunes of the firm and has earned a great deal of respect among his staff. Indeed, if Mr Percy can be persuaded to stay, it is thought that he could also prevent the mass exodus of staff many headhunters expect.
Deutsche has promised to pay bonuses to fund managers but they are almost certain to be low. Any loss of business will not be apparent immediately as it will take months for pensions funds to decide to remove their money, as trustees only meet every few months.
One adviser, Bacon & Woodrow, the actuarial firm, will continue to line up Morgan Grenfell in the "beauty parades" it sets up for pension funds clients.
The business is lucrative for Morgan Grenfell. At the end of December it had pounds 12bn of UK pension fund money under management and pounds 7bn of overseas pensions money.
Sources say Morgan Grenfell has already lost out on three fund management mandates which were being offered in September when the news about Mr Young broke. Morgan Grenfell said it had not lost business.
Mr Young was sacked by Morgan Grenfell in September after investigators discovered he had breached limits for investing in unlisted firms and may have hidden the extent of his investments in Luxembourg holding companies.