'The Gentleman' is back in front of an adoring hometown crowd for the first defence of his maiden world title won with an impressive upset of former training partner Lawrence Okolie on a fairytale night outside at the Vitality Stadium back in May.
Billam-Smith, now signed up for three more fights with Boxxer, will hope to next negotiate a potentially tricky test against an experienced opponent in Masternak, a 36-year-old veteran of 52 professional boxing bouts.
A former European champion, the Polish fighter is perhaps best known on these shores for his battling defeat by Tony Bellew back in 2015.
The 47-5 (31 knockouts) Masternak's only loss since then in his last 12 contests was against Cuba's Yuniel Dorticos in the World Boxing Super Series in 2018.
Now he will attempt to make it a short-lived championship reign for Billam-Smith, who may have been expecting a swift rematch with Okolie.
Instead it seems that 'The Sauce' will look to get back to winning ways elsewhere before accepting the challenge again, with several more huge battles likely looming in a thriving 200-pound division.
As well as Okolie, there is also the small matter of Richard Riakporhe, Billam-Smith's old rival to whom he dropped a split decision back in 2019 - his only loss to date - and who now stands as the WBO's mandatory challenger having withdrawn from purse bids to face IBF title-holder Jai Opetaia earlier this year.
Billam-Smith vs Masternak date, start time, venue and ring walks
Billam-Smith vs Masternak takes place on Sunday December 10, 2023 at the Bournemouth International Centre in Dorset - Billam-Smith's third time headlining the indoor venue.
The main undercard begins at 6pm GMT, with main event ring walks expected at 9pm.
The fight is taking place on Sunday instead of Saturday this weekend so those Bournemouth fans travelling to watch their team play Manchester United at Old Trafford in the Premier League can attend both events.
Billam-Smith vs Masternak fight card/undercard in full
On Sunday's undercard, Olympic heroes Ben Whittaker and Lauren Price both take the next steps on their respective professional journeys.
Michael McKinson is also in action, while Lee Cutler and Obi Egbunike battle for the English super-welterweight title.
Chris Billam-Smith vs Mateusz Masternak
Michael McKinson vs Musah Lawson
Ben Whittaker vs Stiven Leonetti Dredhaj
Lauren Price vs Silvia Bortot
Lee Cutler vs Kingsley 'Obi' Egbunike
Francesca Hennessy vs Lucrecia Belen Arrieta
Lewis Edmondson vs Dmytro Fedas
How to watch Billam-Smith vs Masternak
TV channel: In the UK, Billam-Smith vs Masternak is being shown live via Sky Sports, with the action beginning at 6pm on Sky Sports Arena.
Live stream: Sky Sports subscribers can also watch the action as it happens live online via the Sky Go app.
Billam-Smith vs Masternak prediction
A supremely focused Billam-Smith was superb against the out-of-sorts Okolie, sending his old friend - who delivered a very strange display - to the canvas no fewer than three times en route to a fully deserved decision win seven months ago.
It was the culmination of a lifelong dream at the home of his beloved Cherries for one of British boxing's most affable and likeable figures, who was the sizeable underdog that night against the previously unbeaten Okolie.
This first defence ought to be a good one for Billam-Smith, who should be suitably tested by a savvy, durable and powerful veteran who is competing in a world title fight for the first time aged 36, but who seems unlikely to be able to cause a genuine upset on the night.
Rather, we expect Billam-Smith - three years younger than Masternak - to put on another show and fire on all cylinders from the first bell in front of his hometown crowd once more, dominating the occasion and overwhelming his opponent.
Masternak has only been stopped once as a pro - by Grigory Drozd in Moscow back in 2013 - but history seems likely to repeat itself in Bournemouth if the superior Billam-Smith applies suitable pressure from the off.
Billam-Smith to win via stoppage in the middle rounds.
Billam-Smith vs Masternak weigh-in results
Billam-Smith tipped the scales at 14st 3lbs during Saturday's weigh-in, while Masternak came in at 14st 2lbs.
Billam-Smith vs Masternak betting odds
Billam-Smith to win: 2/7
Masternak to win: 10/3