Springbok fly-half Jantjies provided 16 points and was at the heart of Lions’ play as they ran in seven tries for a bonus-point victory.
Ruan Combrinck opened the scoring in the second minute and doubled his tally at the end of the first half, adding to efforts from Kwagga Smith, Ruan Dreyer and captain Warren Whiteley.
Jan Serfontein and Jesse Kriel got on the board for Bulls, but Franco Mostert’s try three minutes after the restart scuppered their hopes of a comeback.
Lions controlled the rest of the match, but did not add to their score until Lionel Mapoe touched down and Jantjies had the final say, adding the extras with the last kick of the game.
Josh Mann-Rea responded to an early penalty try awarded to the Kings, but a missed conversion and a Lionel Cronje penalty gave the South Africa franchise a five-point lead at the break.
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