Jefferies, 59, was on Friday night back at the club he managed between 1995 and 2000 barely two hours after Csaba Laszlo was given the boot.
"Anything connected with Hearts gets my juices flowing," said the lifelong Jambos fan, who also captained the club during his playing days. "It has been my club."
Laszlo was sacked after 18 months in charge when majority shareholder Romanov finally lost patience with the colourful and outspoken Hungarian.
The controversial Romanov could hardly have acted more swiftly to replace him, prompting suspicions this move had been in the pipeline for a number of days.
Jefferies, who left Kilmarnock less than three weeks ago, insisted he did not get the call until yesterday afternoon, while he was out shopping in Edinburgh.
And he was already planning to surpass Laszlo's record as Romanov's longest-serving boss.
"Everyone appreciates clubs like Kilmarnock, where I had a great time and the supporters were great to me," he added. "It is a major achievement to be at one club for eight years.
"But it does not happen too often, coming back - Walter Smith did it - but we just have to wait and see.
"I hope to be here for two or three years. It will take me a few days and weeks getting to know the players personally. I have a few ideas but I am looking forward to that challenge."
Source: PA
Source: PA