Passengers may have to suffer smelly toilets on Sir Richard Branson's new tilting trains for several more weeks.
Faulty toilets on the Pendolino trains on the West Coast Main Line, operated by Virgin Trains, will not be fixed before the end of June.
The 125mph trains travel from Birmingham New Street to London and also north to Glasgow.
In the meantime, Virgin's managing director Charles Belcher warned in an internal memo: "There may be some uncomfortable journeys if there is warm weather."
The "toilet training" problem, which has included locked loos, spillages and blocked toilets, is one of a number of difficulties to beset the Pendolinos, which were launched in September at a lavish ceremony in London attended by Tony Blair.
Air-conditioning has also been faulty, and one hit a buffer at Liverpool's Lime Street station.
Virgin's other fleet of new rolling stock, the Voyagers on the Cross Country network, were also beset with various technical problems in their first months of operation in 2002.
The 53 Birmingham-built trains cost £1.2 billion including a £600 million maintenance contract at Alstom's recently downgraded Washwood Heath plant.