A legal challenge to overturn the ban on hunting in England and Wales has been launched at the Royal Courts of Justice.
Lawyers for pro-hunt campaigners, backed by the Countryside Alliance, began what could be a long pursuit through the courts by lodging papers seeking judicial review.
These will be studied by a single judge who will have to decide whether there is an "arguable case" which should go to a full High Court hearing.
The bid to overturn the ban is based on claims that the 1949 Parliament Act used to force it through was invalid.
Earlier, Lord Donaldson, one of Britain's most senior retired judges, said in a radio interview the legal case had "100 per cent strength".
The Act was invoked for only the fourth time in 55 years last night, after peers rejected a final opportunity for compromise by voting down a proposal to delay the ban until July 2006.
The ban will now come into force on February 18th, unless the courts intervene.
If the legal challenge is allowed to go ahead it is likely finally to be decided on an appeal to law lords sitting in the House of Lords.
The application for judicial review is in the names of Countryside Alliance chairman and former law student Mr John Jackson; Bicester Hunt member Mr Patrick Martin, from Oxfordshire, and Ms Mair Hughes, wife of the Master of the LLangeinor Hunt who is also a farrier from Gilfach Goch, Mid Glamorgan.