Trailing 10-6 at the break, Blackock turned the tables on their south Dublin rivals after the resumption with captain Gus McCarthy, Ruben Moloney and Oliver Coffey all crossing the whitewash.

After getting on the end of a line-out maul, hooker Zach Baird (younger brother of Ireland international Ryan) dotted down in the 14th-minute to propel Michael’s towards a four-point interval cushion.

However, ‘Rock were a rejuvenated force on the resumption and edged themselves in front with a clinical McCarthy finish over the line.

They looked set for a convincing victory when Moloney and Coffey added converted scores in the 48th and 56th minutes, only for Baird’s second try of the contest to set-up an enthralling finale.

Nonetheless, Blackrock held firm under intense pressure from Michael’s to eventually book their spot in the last-eight.

Scorers for Blackrock College: Tries – G McCarthy, R Moloney, O Coffey (one each); Pens – Z Quirke (2); Cons – Z Quirke (2).

Scorers for St Michael’s College: Tries – Z Baird (2); Pens – F Gunne (2); Cons – F Gunne (2).

BLACKROCK COLLEGE: R Moloney; A Quinn, H Cooney, L Kritzinger, E Walsh; Z Quirke, O Coffey; M Holmes, G McCarthy, P McCarthy; M Colreavy, A Mullan; L Molony, T Brigg, K Jackson.

Replacements: T O’Riordan for Holmes, P Van Zuydam for Cooney (both 68).

ST MICHAEL’S COLLEGE: J Nicholson; L Hassett, S Berman, W de Klerk, C Foley; C McMamee, F Gunne; T Stewart, Z Baird, S Egan; D Woods, D Barron; D Carroll, J White, M Victory.

Replacements: A Murray for Stewart, R Coogan for Egan, M O’Reilly for Barron (all 50), M Sherwin for Baird, J Brown for White (both 63).

Referee: D Blake (LRR).