Ireland lock Donncha O'Callaghan was one of four players added to the Barbarians squad on Monday to face England in a non-cap international at Twickenham on June 1. France fly-half Francois Trinh-Duc, South Africa second row Juandre Kruger and Argentina full-back Juan Martin Hernandez are among the other Test players named in coach Dean Ryan's multi-national array of talent. In all nine countries are represented, with world champions New Zealand boasting six players in a 24-man squad that has a combined 370 caps. Former England forward Ryan, the coach of a Worcester side recently relegated from the English Premiership, was looking forward to working with such a star-studded line-up. "It is a testimony to the special appeal the Barbarians has throughout the rugby world that we have been able to bring together such an experienced and talented squad of players," Ryan said Monday. "It's a privilege to be able to work with a group who have achieved so much and we're looking forward to taking on a young England side at Twickenham next Sunday." There is one change to the group of players previously announced with Castres-bound All Black Sitiveni Sivivatu now unavailable. Sunday's match will be a chance for the England players on show to make a late bid to press their claims for a place in the squad for the next month's three-Test tour of New Zealand. Although not normally accorded Test status, matches for the Barbarians -- rugby union's most famous invitational side -- have traditionally been regarded as a significant honour for the players selected. The Barbarians' most celebrated fixture was their 23-11 win against New Zealand in Cardiff in 1973. Gareth Edwards's opening score, when the outstanding Wales scrum-half finished off a seven-man length-of-the-field move initiated by half-back partner Phil Bennett, is widely regarded as one of rugby's greatest tries. Barbarians squad to play England (country code indicates Test player): Backs: Jimmy Cowan (Gloucester/NZL), Tomas Cubelli (Belgrano/ARG), Hosea Gear (Toulouse/NZL), Juan Martin Hernandez (Racing Metro/ARG), Brock James (Clermont), James O'Connor (London Irish/AUS), Rene Ranger (Montpellier/NZL), Joe Rokocoko (Bayonne/NZL), Benson Stanley (Clermont/NZL), Francois Trinh-Duc (Montpellier/FRA) Forwards: Julien Brugnaut (Racing Metro/FRA), Schalk Ferreira (Toulouse), Mamuka Gorgodze (Montpellier/GEO), Andrew Hore (Highlanders/NZL), Juandre Kruger (Racing Metro/RSA), Alexandre Lapandry (Clermont/FRA), Juan Manuel Leguizamon (Lyon/ARG), Nahuel Lobo (Montpellier/ARG), Donncha O'Callaghan (Munster/IRL), Ti'i Paulo (Clermont/SAM), Sona Taumalolo (Perpignan/TGA), Joe Tekori (Toulouse/SAM), Roger Wilson (Ulster/IRL), Davit Zirakashvili (Clermont/GEO) Source: AFP