Brostaigh took advantage of what appeared a good opportunity at Dundalk in the Irish Stallion Farms EBF Fillies Maiden but only just at odds of 1/3.

The Joseph O’Brien-trained filly, successful in a barrier trial here in August and placed in three of her five starts since, flew out of the stalls and held a prominent position throughout.

Declan McDonogh ’s mount looked set for a reasonably comfortable success heading into the final furlong but newcomer Mna Na Mhi really picked up when switched out to get a clear run and got to within a neck at the line. Chicago Lightening was three-quarters-of-a-length back in third.

O’Brien’s assistant Brendan Powell said, “She got a nice position the whole way around. I thought she was going to go away and do it but the second horse, of Pat Martin's, has come and made us fight for it.

“She's got her maiden win now, for breeding purposes, and we'll see what happens now.

“She deserved to win one and she's done it now.”