Young leg spinner Alex Russell claimed six wickets in his second first-class fixture but Kent go into the final day in a strong position at Wantage Road.
Bell-Drummond finished unbeaten on exactly 300 for Kent, registering the fourth-highest individual score in the county’s history after almost nine hours at the crease as the visitors racked up an imposing total of 621.
That left Northamptonshire, whose leg-spinner Alex Russell recorded figures of six for 175 in only his second first-class game, weighed down by a hefty first-innings deficit of 384 as they went out to bat again.
However, spirited half-centuries by Rob Keogh – his second of the match – and skipper Luke Procter maintained their side’s hopes of avoiding defeat as they reached 214 for five, still 170 adrift, before bad light halted play.
Resuming on 271 overnight, Bell-Drummond survived a strong lbw appeal by Ben Sanderson in the second over of the day and made cautious progress while his partners threw the bat at the other end.
However, wickets began to tumble to the young spinner, with Joey Evison lured down the track and stumped for 27 before Hamid Qadri and Wes Agar also perished in pursuit of quick runs.
With Jack White trapping Matt Quinn leg before first ball, Bell-Drummond, on 293, suddenly looked in danger of ending up marooned with a personal landmark tantalisingly close as last man Arshdeep Singh arrived at the crease.
The India international calmly swung his first delivery over long on for two before smashing a couple of boundaries as Bell-Drummond inched closer to 300 – eventually pulling Russell for a single and punching the air with delight and relief.
Having slammed the next ball into the hands of deep midwicket, Arshdeep raced off to lace up his bowling boots as he and Agar hurtled in for a pre-lunch burst at Northamptonshire’s openers.
They removed both before the interval, with Emilio Gay prodding Arshdeep to Jack Leaning at second slip before the skipper’s call for Joe Denly’s leg-breaks paid dividends as Ricardo Vasconcelos departed in the same manner to the final ball of the session.
Sam Whiteman displayed some resistance after lunch, crunching Agar for successive off-side boundaries to reach 28, but Denly tempted him to sweep and the resulting top edge sailed to backward square.
Denly, who remained on throughout most of the afternoon, might have collected a third wicket when Ben Compton was unable to grasp a sharp chance from Keogh at short leg with the right-hander on 18.
Keogh gradually got on top of Kent’s all-spin attack, taking advantage of some wayward Denly deliveries to crack three fours in an over and sweeping Qadri to the square leg fence to bring up his second half-century of the match on the cusp of tea.
There was a scare for Keogh when a ball from Qadri lodged in his back pad and then trickled across to rest against the stumps without dislodging a bail, but the spinner got his man soon afterwards for 57, winning what looked a very unlikely lbw decision.
That broke the fourth-wicket stand of 80, but Procter progressed to a resolute 50 from 146 balls and, with Saif Zaib going for his shots at the other end, the pair shaved another 51 off the deficit.
The light quickly deteriorated but rather than removing the players from the field, the umpires elected to enforce spin bowling. Leaning brought himself on to bowl and promptly had Procter considered leg before with his second delivery, but shortly after the umpires took the players from the field.