Andrew Lynch and Sizing Europe en route to victory at Cheltenham
Cheltenham's Arkle winner Sizing Europe will face more experienced rivals in the Boylesports.com Champion Chase (1805 BST) at the Punchestown Festival.
Trainer Henry de Bromhead is pitting him against top two-milers Twist Magic, Forpadydeplasterer and Kalahari King.
Twist Magic, for Paul Nicholls, is one of seven British-trained runners who have travelled over by ferry after ash cloud grounded flights from the UK.
Trainers and owners have travelled by helicopter and sea to make the meeting.
The feature race on the meeting's opening day sees Tom Cooper's Forpadydeplasterer bidding to go one better after four seconds on the trot.
The horse, named after a plasterer called Paddy who helped former Irish leader Bertie Ahern out of some financial trouble, was runner-up in the Queen Mother Champion Chase and again at Aintree over two-and-half miles.
He won last year's Arkle Chase at the Cheltenham Festival, his only victory in his last nine starts which have yielded eight second-place finishes in all.
Twist Magic, who won this Punchestown contest in 2008, claimed the Tingle Creek and Victor Chandler Chase this season before disappointing at Cheltenham.
The other British raiders are Ferdy Murphy's Kalahari King, an early casualty at Aintree having finished third in the Queen Mother, and the Nick Williams-trained Cornas.
Golden Silver appears the likeliest contender out of three entries from the Willie Mullins stable.
The five-day meeting's highlight is the Punchestown Gold Cup on Wednesday, in which 2006 Cheltenham Gold Cup winner War of Attrition is set for an emotional racecourse farewell.
He is up against Denman, who memorably beat Kauto Star in the 2008 Gold Cup.
Meanwhile, the travel problems created by the Icelandic ash cloud will hit the number of British racing fans attending the meeting.
Trainers and jockeys will cross the Irish Sea by ferry to ensure their attendance.
Punchestown general manager Dick O'Sullivan said: "We very much value our UK customers and we are disappointed that many of them won't be able to join us this year but heartened by the extraordinary efforts many have made to be in Punchestown this week."