Neither the name of the firm nor the exact amount of the investment have been disclosed.

The new funds have resulted in the exit of the previous syndicate of investors, led by UK private equity house Octopus, which invested in Gyro in 2005. Octopus says it has generated a return of 2.3 times its original investment, or an IRR of 57.7 per cent. Meanwhile Matrix Private Equity Partners, which invested £750,000 in Gyro in 2005, received £2.4 million from the sale, yielding an IRR of 50 per cent.

For Gyro, which has offices in ten countries, the deal will fund further international expansion. The company also intends to branch out through a series of forthcoming acquisitions into PR and data management.

Gyro’s management, led by CEO Gary Brine, will be unchanged following the investment. Brine comments: ‘The investment is a significant step towards Gyro’s ambitions to become the biggest and most successful B2B marketing agency in the world.’

Established in 1991, Gyro’s clients include electronics manufacturer Sony, enterprise software giant Oracle, and sugar mogul Tate & Lyle.

It made four acquisitions in 2007: Manchester-based marketing agency Cicero, Stockholm-based brand communications business Dowell Stubbs, healthcare and biotech specialist Woolley Pau, and healthcare PR firm hsdcommunications.