The Aidan O’Brien Group One bandwagon has a bumper opportunity to get back on the rails this weekend.A total of eight top-flight races are up for grabs between Saturday’s Betfred St Leger at Doncaster and the Irish Champions Festival at Leopardstown and the Curragh. O’Brien is likely to be represented in all of them.Constitution River heads his domestic team in the €1.25 million Royal Bahrain Irish Champion Stakes due off at 5pm on Saturday but prior to that a landmark 10th victory in the 250th running of the world’s oldest classic could be on the cards for the Irishman.Epsom Derby winner Christmas Day tops a handful of Ballydoyle entries left in the St Leger after Monday’s latest acceptance stage. A dozen horses remain in contention, and Joseph O’Brien could provide the biggest threat to his father with both Enceladus and Highwayman among the likely starters. O’Brien jnr saddled Galileo Chrome to win in 2020 and rode his father’s Leading Light to victory in 2013.The last Derby winner to double up in the Leger was Reference Point in 1987 although Christmas Day’s sire, Camelot, was controversially beaten in his 2012 Triple Crown attempt by Encke. The latter tested positive for anabolic steroids the following year.Christmas Day was initially made a 7/4 favourite ahead of his stable companion Pierre Bonnard and Enceladus in a classic picture dominated by the O’Brien family. Another Leger success could propel what shapes as being a vital weekend’s action for any hopes that O’Brien snr can wind up 2026 with a new world record for Group/Grade One victories. He set the current mark of 28 in 2017 and is currently on 15 for this campaign.[ Three sporting events to watch this week: Your handy guide to sport on televisionOpens in new window ]What had seemed like remorseless momentum stalled somewhat in August however when only Sun Goddess in the Phoenix Stakes struck at the highest level. Unusually, the month’s big festivals at Goodwood, Deauville and York weren’t as successful as usual for Ballydoyle. In recent weeks, O’Brien strike rate at home is at 15 per cent. The Leger picture got even more positive for Irish hopes on Monday when Godolphin’s Del Maro was taken out. It leaves a home team headed by the Andrew Balding trained pair Hatteen and Galiyan.As well as Constitution River, leading O’Brien hopes at the Irish Champions Festival are set to include Precise who could take on old rival Blue Bolt in the Coolmore Matron Stakes at Leopardstown before focus switches to the Curragh on Sunday. The season’s top stayer Scandinavia is already a heavy odds-on favourite for the Comer Group Irish St Leger. Sun Goddess and Alpha appear to give their trainer a strong hand in the Moyglare Stud Stakes while Giant Sequoia is at the forefront of betting for the Goffs National Stakes. Royal Ascot winner Mission Central is a Ballydoyle contender for the Bar One Flying Five although it is Donnacha O’Brien’s July Cup hero Comanche Brave tops most ante-post betting lists for the weekend’s top sprint.