The investment banks in charge of arranging the acquisition financing behind Kohlberg Kravis Roberts' record buyout of retailer Alliance Boots have been left holding the senior debt of the deal after failing to sell down the loans to other investors.

Loans worth £5.05bn ($10.4bn) will be held on the bank's balance sheets until they can be syndicated later this year, if market volatility of the last several weeks dissipates, according to a source.