Normandy Ferries eventually supplemented the Dover-Boulogne route with the twin sisters MV Panther and MV Tiger, both former Danish ferries. The Dover-Boulogne route was sold to European Ferries on 4 January 1985 which rebranded them, along with its Southampton–Le Havre route, as Normandy Ferries Ltd. Following the purchase of European Ferries, P&O operated routes from Dover to Calais in France and Zeebrugge in Belgium, initially trading under the Townsend Thoresen brand; however, due to the bad publicity that the Herald of Free Enterprise disaster brought to that brand in March 1987, the services were subsequently rebranded to P&O European Ferries, with most vessels named with the prefix Pride of. Prior to the acquisition, European Ferries had ordered two purpose-built vessels for the Dover–Calais route. These were delivered in June and December 1987 as and , taking on the role of flagships for P&O European Ferries. P&O's Dover operations remained largely unchanged until 1998 when they were merged with Stena Lines Dover and Newhaven operations to form P&O Stena Line (P&OSL) in response to the increased competition from the Channel Tunnel which opened in 1994 and the coming end to duty-free shopping within the EU in July 1999. As a result, vessels were renamed from the recognisable Pride of prefix to instead be prefixed with P&OSL in 1999. P&OSL operated eleven vessels, eight of which provided a freight and passenger service on the Dover–Calais route and the remaining three a freight service on the Dover–Zeebrugge route. In August 2002, P&O acquired Stena Line's 40% share of P&OSL, which were re-merged with the Portsmouth and North Sea operations under the P&O Ferries brand. In December 2002, the Dover–Zeebrugge route closed, leaving only the Dover–Calais route remaining. Vessel prefixes were again changed to PO before they were repainted into a new livery and then resuming the use of the Pride of prefix in 2003. On 8 August 2008, P&O Ferries announced it had placed a €360 million order with STX Europe for two new ships to replace the ageing Pride of Dover and Pride of Calais. The two new vessels, and , are 49,000 gross tons and 210 metres long, making them the largest ferries to operate in the English Channel. They were the first passenger ferries in the world to comply with the new SOLAS "Safe Return to Port" requirements. Spirit of Britain entered service on 21 January 2011 replacing Pride of