The company was first appointed in November 1999 to provide communications advice and support for the construction of a second vehicle tunnel, known as the New Tyne Crossing.
Since 2011, its work has focused on the Grade II-listed Pedestrian and Cyclist Tunnels which closed for refurbishment in 2013 and re-opened to the public in August 2019.
Managing director of the Boldon-based firm, Daniel O’Mahoney, said: “It is highly unusual for a PR company to have such a long association with one client.
“We nursed the New Tyne Crossing from consultation to Public Inquiry as part of the Arup team of expert advisers, then the appointment of contractors, liaison with their PR team during construction and the visit by The Queen in 2012.
“By then, our attention was focused on the Grade II-listed Pedestrian and Cyclist Tunnels which were in a poor state of repair. Much of our work in the early days involved dealing with complaints from users about escalator and lift breakdowns.
“We helped build the case to the then-owners, the Tyne and Wear Integrated Transport Authority (TWITA), to refurbish and restore the tunnels.”