Conversation so far:
When was the rebel season?
In 1990, the unofficial Welsh championship was replaced by a league structure involving promotion and relegation.
Why was the Welsh championship replaced?
Cardiff competed in top flight but could only manage a fourth-place finish in 1990-91, and exited the Cup at the quarter-final stage.
What was their record during the rebel season?
beating league runners-up and Cup champions Llanelli 43-0 at the Arms Park and beating league champions Neath 18-4 away in the last game of the season.

Question: Did they win the championship?
Self-contained rewrite: Did Cardiff win the championship?