Johnson is setting a strong pace in his bid to succeed the retired Tony McCoy, to whom he finished second no less than 16 times in the title race.
In what is his best-ever start to a jumps campaign, Johnson reached the milestone on Easily Pleased (evens favourite) in the Francis Clark Handicap Chase.
However, it was nip and tuck at the business end of the race after Easily Pleased had led from the second fence but was challenged all the way to the line by Dave Crosse on Red Skipper.
Johnson was at his strongest to get Martin Hill’s nine-year-old home by a nose in a bobbing finish.
Earlier Tim Vaughan’s Bells Of Ailsworth (5-2 favourite) had taken Johnson to 49 for the season when regaining the lead at the final flight from Only Gorgeous and going on to take the NewtonAbbotRace On Twitter Maiden Hurdle by two lengths with the other four runners well in arrears.