Maritime history will be made in Southampton Docks when the Princess Royal and her daughter, Zara Phillips, perform a unique double naming ceremony tomorrow.

P&O Cruises' vessels Oceana and Adonia will officially enter service after a spectacular dockside event in the evening, culminating in a huge fireworks display over the port.

Already dubbed Southampton's White Sisters, the 77,499-ton ships will operate alongside P&O Cruises' already established vessels Oriana and Aurora.

Previously part of the Princess Cruises' American-based fleet, Oceana was formerly known as Ocean Princess while Adonia was Sea Princess.

The Princess Royal is no stranger to naming ships as it was in April, 2000 that she was in Southampton to christen Aurora.