Mr Roberts must pay the court costs estimated at £600,000
A man who bought a series of ancient titles has won the right to a half share of any ship wreck that washes up on part of Pembrokeshire's coast.
Mark Roberts bought the Lordships of Trevine and the City and Suburbs of St David at auction in 2000.
A High Court judge ruled a right that went with the titles was not extinct as some had thought and he was entitled to wreck that fell within his manor.
However, he will have to pay the estimated £600,000 the case has cost.
The judge trawled through history, back to before the Norman conquest, in arriving at his ruling.
Mr Justice Lewison said that Mr Roberts was entitled to a "moiety" - half of all wrecks that are cast onto the foreshore of stretches of the Pembrokeshire coastline that fall within his manors.
Mr Roberts had asked the judge to grant him a wider order, entitling him to "rights of wreck" over almost 30 miles of coast, stretching from Newgale, right round the peninsula of St David's Head and on past Strumble Head to the port of Fishguard itself.
Relying on pre-1066 "Welsh customary law" - and tracing his title back to the ancient Bishops of St Davids and a charter of King Henry 1 in 1115 - he also sought exclusive fishing rights along the foreshore, rights of treasure trove, sporting rights and even ownership of stray animals.
His lawyers argued that all of these, and other ancient rights, had not been extinguished and were the rightful possessions of Mr Roberts, who also holds the title of Lord Marcher of St Davids.
Mr Justice Lewison rejected Mr Roberts' wider arguments, concluding that the foreshore had never belonged to the Bishops of St Davids and all but one of the rights he claimed were not "exercisable over the foreshore".
Rights of treasure trove, in particular, were exclusively the Crown's.
However, despite the passage of almost 900 years since the Royal charter of 1115, the judge said nothing had removed the entitlement of the successors of the Bishops of St Davids "to the exercise of the right to a moiety of wreck".
He concluded: "Mr Roberts is entitled to that right in his capacity as Lord of the Manor of Trevine and as Lord of the Manor of the City and Suburbs of St Davids in so far as wreck is found on the foreshore adjoining those manors."
Having lost many of the arguments in court, Mr Roberts was ordered to pay the legal costs of the four-day case.
The judge was told that Mr Roberts' legal team had run up bills of almost £100,000 and the Crown Estate commissioners put their costs at £570,000 - although that figure is expected to be contested by Mr Roberts.
The judge ordered Mr Roberts to pay £150,000 interim costs before 15 September.
The final figure he must pay will be assessed at a later date.
In opening his judgement, Mr Justice Lewison said his researches into the case had gone back at least half a century before 1189, the year in which King Henry II died and which "is generally regarded as the beginning of legal memory."
Mr Roberts declined to comment after the hearing.