The tone had been set by the Tannoy man before kick-off. "Have Chelsea got the fight for it," he asked as the teams took the field. "Have they got the bottle?" In the end Claudio Ranieri's side showed enough of those qualities, but it was nerve-janglingly tight.
Three goals ahead after 25 minutes, Chelsea tottered in typical away fashion to inject drama into a tie that had been heading for anti-climax. Not until Eidur Gudjohnsen scored their fourth deep into injury-time was Gillingham's stirring recovery killed off.
The First Division team deserved their ovation at the finish, but it is Chelsea who can look forward to a fifth-round tie at Arsenal.
"I have heard a lot about the FA Cup and everything I have heard was true," reflected Jesper Gronkjaer, scorer of two goals on an impressive first start for Chelsea. "It was very difficult. You saw what happened in the second half."
Those who wondered whether Chelsea had thrown away £7.8 million on Gronkjaer after the long, injury-laden wait that followed his move from Ajax were treated to a fine performance as the 23-year-old flitted from flank to flank and scored twice.
With Eidur Gudjohnsen bustling menacingly around him, the holders looked in little danger. If there was no doubting Gillingham's fight, it seemed they had lost their bottle on the big occasion.
Yet led by their indefatigable captain, Paul Smith, and helped by the introduction of the muscular Iffy Onuora at the interval, they produced a memorable fightback. First Paul Shaw and then Onuora pounced, and for the last 25 minutes Chelsea held out nervously as the decibel levels rose among an excited crowd.
Frank Leboeuf, who was later carried off, had played a role in Chelsea's opener, his long ball culminating in Barry Ashby misdirecting a header back to Vince Bartram, which allowed Gudjohnsen to nod the ball into an empty net.
When Gronkjaer scored twice in 10 minutes after a spell of Gillingham pressure, first running on to Gudjohnsen's pass and cutting in to score with his right foot, and then latching on to a Gianfranco Zola pass that caught out Chris Hope and scoring with his left, it seemed game over.
But nothing is straightforward on Chelsea's travels. Shaw slid in the loose ball after Onuora's run had been stopped, and 15 minutes later Onuora headed in after Carlo Cudicini had parried Nicky Southall's free-kick.
But the chance they craved never arrived and Chelsea could finally relax when Gudjohnsen volleyed in Graeme le Saux's cross.
Gillingham: Bartram, Edge, Southall, Ashby, Pennock (Patterson 67), Hope, Smith, Saunders, Lewis (Onuora 45), King, Shaw (Thomson 89). Subs Not Used: Gooden, Browning. Booked: Ashby, Patterson. Goals: Shaw 51, Onuora 67.
Chelsea: Cudicini, Leboeuf (Le Saux 66), Melchiot, Ferrer, Terry, Morris (Stanic 77), Gronkjaer, Harley, Wise, Zola (Poyet 45), Gudjohnsen. Subs Not Used: de Goey, Hasselbaink. Booked: Morris. Goals: Gudjohnsen 3, Gronkjaer 14, 24, Gudjohnsen 90.
Referee: D Gallagher (Banbury).
