Sir Henry, the legendary trainer who won a record 75 times at Royal Ascot, died of cancer on Tuesday at the age of 70.
His widow Lady Jane Cecil was granted a temporary licence by the British Horseracing Authority, with five runners sent out at Leopardstown, Newbury, Nottingham and Yarmouth.
And it was Morpheus who brought a tear to the eye as Frankel’s half-brother romped home in the final furlong to win by four and a half lengths over Elsiniaar.
"He did it so well,” Lady Jane said afterwards. “He has taken time to get his act together, but that was very pleasing, wasn't it. And (jockey) James (Doyle) gave him a great ride.”
Doyle, who wore a black armband, said: "It is nice to be part of that. Sir Henry was a trainer I've always admired. I was hoping one day I'd get a ride for the stable."
That was not it for Warren Place Stables as, 10 minutes later, Songbird impressed in victory at Yarmouth, winning the Fillies’ Handicap under Ian Mongan.
Mongan’s career highlight was also on a Cecil horse, when he won the 2011 Juddmonte International at York on Twice Over.
"He gave me chances like no other trainer would. If I wasn't riding for Henry, I wouldn't be riding. I have him to thank for that,” Mongan said.
"He always made jokes. He'd always slap you on the head and things and it was fun.
"Life goes on and Warren Place goes on. We're still up there having winners and fingers crossed we get a winner at (Royal) Ascot for him. It would be fantastic."
Knighted in 2011 for his services to horse racing, Cecil was responsible for 25 British Classic winners and ranks among the greatest trainers of all time.
From an aristocratic background, Cecil first took out a training licence in 1969 and celebrated his first British Classic win in 1975 with Bolkonski - ridden by Italian jockey Frankie Dettori's father Gianfranco - in the 2,000 Guineas at Newmarket.
He trained four Derby winners - Slip Anchor, Reference Point, Commander in Chief and Oath - as well as six 1,000 Guineas and four St Leger winners.
Slip Anchor, owned by Lord Howard de Walden and ridden by American jockey Steve Cauthen, turned in one of the great performances to win at Epsom by seven lengths in 1985.
In his later years, the 10-times champion trainer looked after Frankel, the highest-rated racehorse in the world who was unbeaten in 14 starts before retirement last year with almost £3 million in earnings from 14 victories.
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