The country allocated to provide the referee for a championship match is supposed to appoint its No 1 official: in Wales's case Derek Bevan, who refereed the 1991 World Cup final. But as he was in charge of Scotland v Ireland last month (a world-record 26th Test for him), that is his lot for this season.
Thomas is No 3, but then so is the much-criticised Didier Mene of France, who took Wales v England. Bevan will be on the line instead of in the middle at Lansdowne Road, just as Patrick Robin and Patrick Thomas were in Cardiff, and just as Jim Fleming and Stephen Hilditch, Scotland's and Ireland's best, have been this season.
The WRU's referee development officer, Ken Rowlands, himself a former international referee, said: "There was an agreement with the Five Nations that wherever possible they would put their best referee forward. Wales in particular followed this line.
"This season, where every nation has been crying out for this to happen, we have a situation where France pick their World Cup referees before the Five Nations, and do not appoint them to the championship. In Scotland, their most experienced referee is Jim Fleming, yet he hasn't done one of the Five Nations matches.
"In Ireland, Steve Hilditch is their leading official, but they gave a first cap to David McHugh, and Brian Stirling is doing England-Scotland. In England, they have introduced two new referees for both matches involving Wales." As for Wales, their next most experienced Test referee after Bevan is Yeman, who has had all of two caps. Pity the poor players.
Ieuan Evans yesterday singled out Gavin Hastings as the man who makes Scotland tick, and the main danger to Welsh hopes of a first win at Murrayfield since 1985. The two captains and Lions team-mates will be in opposition tomorrow, when the Scots attempt to keep their Grand Slam wagon rolling, while Wales look for their first win of the championship.
"Gavin has been the rock on so many of Scottish and Lions' victories over most of the last decade," said the right wing, who has scored a record 21 tries for Wales.
"His last two performances against Ireland and France were superb. He gives them an air of confidence and when the ball is put behind the pack, they know he is there.
"I was going to say he is as safe as a bank - but maybe that would be the wrong way of putting it at the moment!"
The Welsh fly-half prospect, Arwel Thomas, has signed to play for the Courage First Division club Bristol next season. The 20-year-old student, who plays for Neath, will be available for his new club from late October, provided he proceeds with the move. Bristol failed last year in their attempt to sign the Scotland and Lions fly-half, Craig Chalmers.