Coach Dan van Zyl would have warned against the spectre of complacency given Ulster’s poor recent history in this competition.
Leinster looked to get out of the blocks sharply and let their forwards, led by captain Luke Thompson, take the fight to their hosts.
They were merciless in their approach, right wing Matthew Jungmann exploiting the short side for the opening try and scrum-half Shane Murphy converting as early as the fourth minute.
The solid work of the forwards was rewarded when second row Fionn Gilbert burst over for Murphy to add the extras in the 15th minute.
The impression that the back three looked dangerous on the ball was supported by full-back Diarmuid Egan’s finish down the left hand side for Murphy to convert.
The one-way traffic continued with a penalty from Murphy on the half hour.
Then, Leinster raided down the right-hand side for wing Josh O’Connor to show his pace for Murphy to stretch the lead to an unassailable 31-0 lead at the break.
Thereafter, the accuracy suffered from multiple replacements as Leinster cleared the bench as Gilbert showed up to sell two dummies for his second try.
The game was closed out by replacement prop Jordan Kelly, Murphy making it six out of six conversions to round off an impressive start to the three-match campaign.
In truth, the Clubs have been showing improvement in all their preparatory games and this was proof positive that they are on the right road.
“We had Belvedere College, The Exiles and Blackrock College in the lead-in to the series,” said Team Manager Louis Magee.
“Blackrock was probably the defining one for us, winning that game gave us a decent standard to work from.
“We stuck to our game plan to keep width on our game and work through our processes.
“We made few mistakes in very wet conditions and had the game in hand at half-time.”
Coach Van Zyl will take the show on the road out west to Connacht in Galway next Saturday where the plan is to keep on doing what they have been doing.
“We can’t get too ahead of ourselves. We will focus on Connacht. They are always tough at the Sportsground.”
At Armagh RFC – ULSTER 0; LEINSTER 45 (F Gilbert 2 tries; M Jungmann, D Egan, J O’Connor, J Kelly try each; S Murphy pen, 6 cons).
Ulster U18 Clubs
15. Nathan Jeffers (Rainey)
14. Ciaron Wilson (Carrickfergus)
13. Peter Cullen (Randalstown)
12. Ben Moxham (Larne)
11. Alan Thompson (Coleraine)
10. Matthew Hamilton (Malone)
9. Nathan Rogers (Armagh)
1. Niall Preston (Virginia)
2. Ciaran McGlone (Rainey)
3. Seif Eldin Abd El Gawad (Carrickfergus)
4. Stephen Kelly (Inishowen)
5. Conor McMenamim (Letterkenny)
6. Sam Murray (Armagh)
7. Charlie Clarke (Rainey, Capt)
8. Phil Campbell (Ballymena)
16. Eoin Macdonald (Randalstown)
17. Adam Marley (Finn Valley)
18. Harry Mawhinney (Ballyclare)
19. Robbie Mathers (Banbridge)
20. Matthew Sands (Newry)
21. Ashley Tweed (Ballymoney)
22. Rory Maginty (Letterkenny)
23. Finlay Walker (Ballymena)
Leinster U18 Clubs
15. Diarmuid Egan (Tullamore)
14. Matthew Jungmann (Seapoint)
13. Luis Faria (Wanderers) / Thomas O’Brien (Skerries) 35 mins;
12. Karl Martin (Boyne)
11. Josh O’Connor (Wexford Wanderers)
10. Paddy McKenzie (Wicklow) / Adam Nealon (DLSP) 46 mins
9. Shane Murphy (Skerries) / Jack Ussher (Suttonians) 45 mins
1. Marcus Hannon (Clane) / Sean O’Rourke (Athy) 52 mins
2. Barry Ryan (Wexford) / Mark Nicholson (Wicklow) 46 mins
3. Michael Power (Clontarf) / Jordan Kelly (Enniscorthy) 45 mins
4. Fion Gilbert (Clontarf)
5. Sam Porter (Wicklow)
6. Brian Deeney (Wexford Wanderers) / Robert Murphy (Gorey) 45 mins
7. Luke Thompson (Wicklow, Capt)
8. David Murphy (Blackrock College) / Tadgh Butler (Kilkenny) 20 mins
Leinster U18 Clubs fixtures
Saturday, 9th September: Ulster 0 Leinster 45, Armagh RFC, KO 1pm
Saturday, 16th September: Connacht v Leinster, The Sportsground, KO 2.30pm
Saturday, 23rd September: Leinster v Munster, Donnybrook, KO 12pm