Letterkenny man Mark English produced a huge breakthrough as he ducked under one minute and 45 seconds for 800m for the first time on Friday evening.
English justified his inclusion in the event at the prestigious London Anniversary Games as he finished a brilliant sixth in 1:44:84.
The time, a World Championship A standard, improved his recently-set personal best by .48secs.
Roseanne Galligan set a new Irish women's 800m record at the meeting.
Kildare woman Galligan broke Sonia O'Sullivan's 19-year-old Irish mark by .11 as she clocked 2:00.58 to finish sixth in a race won by the USA's Brenda Martinez in 1:58.19.
Galligan's time improved her personal best by .49 and was the second time that she has bettered the World Championship B standard this season.
In the men's race, English was at the back of the field as pacemaker Matthew Scherer produced an opening lap of 49.54 seconds but the Donegal man moved past a number of athletes in the closing 400 metres.
American Nick Symmonds took victory in 1:43.67 ahead of his compatriots Duane Solomon (1:44.12) and Brandon Johnson (1:44.19).
Kenyan Job Kinyor (1:44.35) and Tyler Mulder (1:44.72) were also in front of the fast-finishing Irishman while those behind him included British duo Michael Rimmer and Mukhtar Mohammed and Poland's Adam Kszczot.
English's time was only .02 outside the Irish record set by David Matthews in 1995.