Fly-half Cliven Loubser ended the game with 22 points, while Chrysander Botha and Louis van der Westhuizen scored two tries apiece, as Namibia ran in seven tries in all.
Victory means the hosts edge out Kenya to both Gold Cup spoils and a place in Pool B in Japan, alongside defending champions New Zealand, South Africa and Italy.
The defeated Kenyans will get the chance to join them in that pool when they contest the four-team global repechage tournament in Marseille in November.
Morocco, meanwhile, have been consigned to life in the Silver Cup next year after they lost their relegation decider against Tunisia 36-13.
In the day’s opening game Zimbabwe made sure of their place in the Gold Cup for another year with a 38-18 win over Uganda in Kampala.
Namibia began this winner-takes-all clash in confident fashion, and Loubser appeared to settle any home nerves in Windhoek with a fifth-minute penalty.
But if the hosts thought they would cruise to victory, and their place at Japan 2019, they received a sharp wake-up call nine minutes later as Kenyan sevens star William Ambaka scored in the left corner. Isaac Adimo added the touchline conversion and the visitors led by four.
Unperturbed, Namibia set a course for the Kenyan 22. Following a near 10-minute assault on the visitors’ line their resolve was broken by Botha, who latched onto a spill of possession from Darryl de la Harpe and cruised through the wrong-footed defence.
Less than three minutes later, Namibia stretched their lead further as Kenya’s struggles under the high ball were punished when captain Davis Chenge lost control of a clearing kick and the resulting attack ended with Van der Westhuizen burrowing over.
Kenya’s Darwin Mukidza then saw a long-range penalty attempt sail wide of the left-hand upright, before Loubser raced over in the left corner to ensure the hosts finished the half firmly in the ascendancy.
Kenya’s hopes of automatic Rugby World Cup qualification received a further blow within two minutes of the restart as Van der Westhuizen scored his second try of the game.
Loubser then extended Namibia’s lead with a penalty, before Ambaka raced onto a grubber kick by Adimo and beat three defenders to score a brilliant try and give the visitors hope.
Namibia, though, reasserted their dominance within a minute as Mahepisa Tjeriko powered over from close range.
The hosts’ victory was rubber-stamped just past the hour mark when Ambaka collided with Johan Tromp as they raced for a bouncing ball on the Kenyan goal-line. Referee Egon Seconds awarded a penalty try and sent the visitors’ star man to the sin bin.
Kenya rallied with 14 men and scored a try through replacement second-row Malcom Onsando, but the title – and automatic qualification – had long gone.
Botha profited from a Janco Venter intercept to take Namibia past the 50-point mark, before the visitors grabbed a fourth try through Mohammed Omollo.
Tunisia began what was effectively a relegation play-off above their visitors and needing only a draw to guarantee their place in the Gold Cup in 2019.
It took Jaco Stoumann’s side less than two minutes to make their home advantage pay as prop Achraf Ben Hammouda powered over the line.
Morocco were not overawed by that early setback, however, and levelled the score three minutes later when Deblaoui Bachir snagged an intercept and ran in from 20 metres.
Tempers flared on the 20-minute mark as Tunisia centre Haitham Chelli and Morocco second-row Lahlali Mohamed were both sent to the sin-bin following a brief altercation.
Morocco fly-half Naoufal El Kadri spurned the chance to give his side the lead from the resulting penalty, but the visitors did take the lead within three minutes as Alexandre Bougja touched down after Tunisia had failed to clear their lines.
Tunisia hit back through captain Sabri Gmir, but despite having captain Yahya Graa sin-binned and seeing El Kadri edge Morocco back in front with a penalty, the hosts made full use of the final play of the first half.
Kicking a penalty of their own to the corner, a forward drive took Tunisia up to the Moroccan line where Chelli atoned for his earlier yellow card to help give the hosts a 17-13 half-time lead.
After the break, Tunisia turned the screw, scoring two tries in the opening 13 minutes of the half, via impressive winger Chedi Jabri and a penalty try as their dominance in the scrum told.
Consigned to their fate, and with rain teeming down, the wind went out of Morocco’s sails and Tunisia added gloss to their win as Ben Hammouda dotted the ball against the base of the post for his second try.
Zimbabwe needed a first victory in this year’s Gold Cup to be sure of avoiding relegation, but fly-half Lenience Tambwera spurned an early chance to give them the lead from the kicking tee.
Uganda were unable to clear their lines, however, and invited further pressure when Robert Aziku was sin-binned for a dangerous tackle in the fifth minute. Their visitors wasted little time in claiming the game’s first try as Connor Pritchard danced over the line less than 60 seconds later.
The hosts held out for the rest of the 10 minutes, though, and the momentum of the match looked to be turning their way before another yellow card – shown to scrum-half Aaron Ofoyrwoth after he tackled Pritchard in the air – created an overload in defence that Tafadzwa Chitokwindo gleefully exploited.
Uganda needed someone to step up, and back-row Byron Oketayot did exactly that as he took advantage of a rolling maul to get the hosts on the scoreboard within two minutes. A Phillip Wokorach penalty then narrowed their deficit to just four points.
However, on the stroke of half-time, Brendon Mandivenga intercepted Robert Masendi’s attempted pass to score Zimbabwe’s third try of the match.
Masendi was substituted at the break, but Uganda’s fortunes failed to improve without their fly-half as Chitokwondo scored his second try of the game.
The hosts reduced the arrears thanks to a Michael Okorach score in the right corner, and after Zimbabwe replacement prop Kudakwashe Nyamufaringwa saw yellow, a Wokorach penalty drew them to within six points.
But it wasn’t to be the hosts’ day, and late tries from Shingi Katsvere and Shayne Makombe put the seal on Zimbabwe’s salvation and denied Uganda a losing bonus-point.
“This is a good step on our 2023 plan and (towards) winning the Gold Cup next year,” man-of-the-match Zimbabwe scrum-half Ernest Mudzengerere said afterwards.
Chituyi, the two try hero in the 45-36 win over Zimbabwe on 30 June, missed last weekend’s 67-0 win over Tunisia through injury alongside former Kenya Sevens international Ayange who was recovering from the effects of root canal while Lilako also returns for the first time since the Zimbabwe match.
Commenting on their inclusion, Head Coach Ian Snook said, “Dallo is in as we have a 6 (forwards)/2 (backs) bench this game.”
“It has been crucial in a couple of other games with fresh forwards coming on late in the game and making a telling difference.
“We hope this will be the same. Felix is on the bench as he can cover many positions and is competent in them all.
Ambaka scored a brace of tries on his test debut as Kenya Simbas mauled Tunisia 67-0https://t.co/fhTLuIgzX9— Game Yetu (@GameYetu) August 11, 2018
“He is a tough competitor and we know he will be up for the physical battle. Biko who usually fills this role is carrying an injury.
“Curtis is back in so we can utilize his experience and cool head late in the game.”
Snook also talked about his expectations from the match against Namibia.
“Our hopes and aspirations is that we play really well and piece together 80 minutes of what has only been seen for 40 or so minutes in the other games,” he said.
“It has been difficult with no warm up games and going in cold for one off test matches. The Tunisian game provided a bit of everything which the players will learn from.
“I’m expecting that the players are ready for an 80 minute effort and are really looking forward to it.”
Kenya squad to play Namibia
Isaac Adimo (Kenya Harlequin), Martin Owilah (KCB), Samson Onsomu (Resolution Impala Saracens), William Ambaka (Kenya Harlequin), Darwin Mukidza (KCB), Tony Onyango (Menengai Cream Homeboyz), Peter Kilonzo (KCB), Oliver Mang’eni (KCB), Jacob Ojee (KCB), Mohamed Omollo (Menengai Cream Homeboyz), Felix Ayange (Kabras Sugar), Dalmus Chituyi (Menengai Cream Homeboyz), Curtis Lilako (KCB), Peter Karia (KCB), Elkeans Musonye (Strathmore Leos), George Nyambua (Kabras Sugar), Andrew Chogo (Kabras Sugar), Malcolm Onsando (Kenya Harlequin), Patrick Ouko (Menengai Cream Homeboyz), Moses Amusala (KCB), Joseph Odero (Kabras Sugar), Colman Were (Kabras Sugar), Davis Chenge (KCB, Captain)
Namibia are four points ahead of Kenya with a superior points difference heading into the decisive match in Windhoek (KO 16:00 local time) and a bonus point will be enough to claim the Rugby Africa Gold Cup title and a place in Pool B at Japan 2019 alongside New Zealand, South Africa, Italy and the repechage winner.
The loser on Saturday will remain in Rugby World Cup 2019 contention, but will need to win November’s repechage in Marseille where they will meet Canada, Hong Kong and Germany.
In the weekend’s other match, Uganda defeated Morocco 47-29, but Kenya’s bonus point win win ended Ugandan hopes of a repechage place
World Rugby will be providing LIVE streaming of the decisive Namibia v Kenya match on Saturday across its digital and social channels.