Andrew Balding and Oisin Murphy teamed up to land the feature Betfred Blue Riband Trial at Epsom on Tuesday.
The King Power Racing-owned son of Sea The Stars looked to have something to find with the principles on official ratings, but seemingly improved plenty for the step up to a mile and a quarter for the first time when running out a ready winner of the Listed Derby Trial.
Always positioned towards the fore under Oisin Murphy on his first outing since landing a Newmarket maiden in September, Bellum Justum travelled up powerfully rounding Tattenham Corner before quickening on past the front-running 4/5 market leader Chief Little Rock to put his seal on the race in the Epsom straight.
Roger Varian's Defiance ran on well to grab the runner-up spot but never really looked like getting past the winner, who stayed on strongly to claim the prize by three parts of a length.
Although no horse has completed the Blue Riband Trial – Epsom Derby double since Blue Peter in 1939, Balding believes his three-year-old deserves his place in the line-up should things go well in his next assignment – the Dante Stakes at York.
"He showed some promise last year but had a little setback about a month ago," explained Balding.
"I think he is bound to come on for the run and we thought that whatever happened today, we would go to the Dante Stakes next and see where we are with him.
"Obviously, I need to talk it over with the owners but if all goes well there then the Derby would be the plan.
"He is very well-balanced and professional and will improve a lot for today. He has really come on in the last fortnight. Oisin was impressed with the way he galloped out.
"It is nice to have an exciting horse for the owners, who have been such big supporters of the yard. Bangkok and The Foxes didn't quite come up to the mark, but I know they would love to have another go (at the Derby)."
Paddy Power cut Bellum Justum to 25/1 from 50s for the Classic following the smooth reappearance triumph.
