Brunswick partner Jon Coles said Errock had quit the firm because he was 'looking for a quieter lifestyle'.
Coles said Errock had run a five-strong research team at Brunswick, devoted to managing the agency's cuttings database.
While Brunswick PROs are usually expected to conduct their own research, research departments at financial comms firms often provide additional information. This could include research on a company pitching for PR support or providing information on another company making a hostile bid for a client.
Errock joined Brunswick in 2000 after 12 years at investment bank Credit Suisse First Boston.