BRILLIANT sunshine bathing Irish racing headquarters yesterday gave supporters of French Derby winner, Fernando, added confidence that he will win his showdown against the winner of the English equivalent, Commander In Chief, in today's Irish Derby. Hernando dispatched his rivals in the Prix du Jockey Club with virtually the same ease as Commander-In-Chief did to his outclassed rivals at Epsom, where he gave Hongkong winter visitor Mick Kinane his biggest career victory. But Kinane, who has had an amazing winning run in the early part of the Irish season, will be taking a rear view look at Commander In Chief at the Curragh, where he partners Massyar for trainer John Oxx. Pat Eddery will ride Commander In Chief. Kinane, and most other observers, believe that the ground at the Curragh could play a significant part in the outcome of the Classic. ''The Commander does appreciate cut in the ground and he will almost certainly get that with the recent weather. But the other fellow does his best on fast ground and I think he would be a very real threat if the ground did come up firm,'' said the Irishchampion. At yesterday's pre-Derby Curragh meeting the going was on the soft side of good but sun, wind and overall drying weather suggest that the going today will be nearer good. Curragh manager Jim Marsh, a former chief stipendiary steward of the Royal Hongkong Jockey Club, has been on the course daily and said: ''There was some rain on Friday after some good weather. I would say that there has to be some cut in the ground but it should really suit most horses.'' Latest betting here is, at best, evens on Commander In Chief and 7-4 Hernando. There is modest support for Prince Khalid Abdullah's second runner behind the favourite, Regency. Kinane's mount, Massyar, is the best of the home brigade but the chances of the 34-year-old champion celebrating a double Derby triumph in 1993 look fairly remote.