Two excellent strikes from Son Heung-min and an opening goal from Arnaut Danjuma were enough to beat Preston and send Tottenham into the FA Cup.
Spurs were frustrated by their Championship opponents until the 50th minute, when Son went flying from 30 yards.
The South Korea international then turned and finished smartly to double the lead in torrential rain.
Danjuma, on loan from Villarreal this week, completed the scoring after coming on as a late substitute.
Antonio Conte’s side advance to the fifth-round draw, which will take place on Monday evening.
Stimulates the spit in life in hard-working Preston
Conte made seven changes to the Spurs starting XI which beat Fulham 1-0 in the Premier League on Monday, including leaving Harry Kane on the bench.
Kane is aiming to become Tottenham’s all-time leading goalscorer and is level with Jimmy Greaves on 266 goals, but had battled illness this week, missing training on Wednesday and Thursday.
Alongside him on the bench was new signing Danjuma, but Spurs’ squad still contained first-team squads such as Son and Dejan Kulusevski – and they started the game on the right foot.
Kulusevski had a shot brilliantly blocked by midfielder Ryan Ledson while home keeper Freddie Woodman made two fine saves thanks to Son’s long-range efforts.
They had more than three-quarters of possession in the opening 20 minutes, but Preston grew into the game and began to restrict Spurs as the game progressed.
A three-man midfield of Ledson, Ben Whiteman and Ali McCann gave Rodrigo Bentancur and Yves Bissouma little time or space to create, as Spurs looked increasingly direct without their captain who had scored 14 goals in his last 14 appearances.
The quality of the threads proves the difference
It took until the opening minutes of the second half for Preston’s resolve to be broken, with Son shooting a quality moment to remind fans why he was the Premier League Golden Boot winner last season.
His seventh of this campaign was arguably his best as he found space from 30 yards before curling an unstoppable strike past Woodman.
Preston upped their game after falling behind and gave Spurs a much tougher test than when they last met – a 5-1 loss in a 2009 EFL Cup meeting.
Son then killed the game after 69 minutes, spinning Jordan Storey after receiving a pass from Ivan Perisic and shooting past Woodman.
Conte was then able to switch teams, including making his Danjuma debut – while Kane was able to remain an unused sub.
And Danjuma, who signed for Spurs after appearing close to joining Everton, scored 15 minutes into his first appearance by netting a low cross from Kulusevski before celebrating with away fans.
