Their gold in the mixed synchronised 3m springboard diving was the 13th medal scored by Scotland at the Sandwell Aquatic Centre, beating their previous Commonwealth Games record in the pool from 16 years ago in Melbourne.
Reid and Heatly also brought up Scotland's half century of podiums across all events, as well as securing the nation’s 13th and final gold medal at the 2022 Games, but the duo admitted they felt the pressure.
The partnership won bronze in the event at the recent World Championships in Budapest and knew they'd been pegged as the ones to beat in the ten-team final.
Diving first, they set the standard in a closely fought competition with little margin for error, finishing just under two points ahead of Australia's Shixin Li and Madison Keeney.
For Reid, 26, the primary emotion was relief, after she finished fourth in the defence of her 1m springboard title from the Gold Coast last week.
"We had some disappointments earlier this week so to end on that note, I'm just so happy, it's going to take a while to sink in," she said.
"I certainly don't mind sharing this one with James. Having him as an anchor point when I was feeling quite jittery helped me so much.
"I knew there was expectation on me, you can't escape that and have to embrace it really. We really felt the pressure but winning sometimes feels better when you've come through a few setbacks.
"It's hard in front of an English crowd sometimes, especially as we were following their divers, but the support was incredible. We rivalled them in noise and that really makes a difference. It's a moment in my career that I'm going to look back on very fondly."
After three fourth places in recent days Heatly, 25, admitted the pressure was on.
He'd just missed the medals in the 1m and 3m springboard and the men's synchro competition but always knew the best could be saved to last.
And there is little time for any rest, the partnership will now have one day off before jetting to Rome for the European Championships later this month.
"It's international sport, it's about who copes with the pressure, but it has been a tough few days," he admitted.
"Grace and I have a great relationship and winning the bronze at the Worlds meant we knew the expectations were there. On paper we were the ones to win it, but the Australian weren't in Budapest, so it was hard to know what to expect.
"We just tried to block that out and focus, we were what we were capable of, but you've still got to do it."
Scotland brought a full-strength diving team to Birmingham, but the pressure was always going to be on Reid and Heatly, following their medals four years ago and world success, to lead the efforts.
However, the signs of future promise are there to see with Angus Menmuir and Gemma McArthur, ranking seventh in the mixed synchro platform final, won by England's Noah Williams and Andrea Spendolini Sirieix.
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