A High Court judge today refused to halt a planned Boxing Day strike by Tube drivers embroiled in a pay row.
London Underground (LU) bosses had asked Mr Justice Eder to stop industrial action, during a High Court hearing in London which began yesterday.
They said the Aslef union called the strike in breach of trade union legislation by balloting members not rostered to work on Boxing Day.
Aslef, which wants extra Boxing Day pay for drivers, said the strike was lawful and should not be stopped.
The judge announced that he was not going to grant an injunction halting the strike and said he would give his reasons later today.
Later Mick Whelan, Aslef's general secretary, said: "We are incredibly pleased. We believe this is the right decision."
Mr Whelan added: "We are very pleased we have won this case, but we regret that we have spent the last two days in the High Court instead of sitting around a negotiating table trying to work out a settlement."
Howard Collins, Chief Operating Officer of London Underground, said they would consider whether to appeal once they had the judge's reasons for his decision at about 4pm today.
"The judge has done the right thing and told both parties early but cannot give us the reasons, and we need them to understand whether an appeal is worth pursuing.
"At that point we and our legal team will consider them and, if we believe we have a strong case, we will appeal.
Mr Whelan said that, if the court had accepted the arguments for granting the injunction, it would have made it "incredibly difficult for any trade union to have a ballot for industrial action in the future".
Mr Whelan said he regretted having to spend time in court when he could have been in talks seeking to resolve the industrial dispute.
He said: "Some valuable time has been lost."