Jakobsen was brought into the Cradley team part way through the 1987 season following Alan Grahame's diagnosis and subsequent lay-off with Hodgkins disease. At 21 years old, he arrived with an impresive pedigree, but gave the rest of the league a few weeks start.
The tall 'Jacko', as he was known, was Danish Junior Champion in 1984 and already a Nordic Finalist in '87 when he joined the Heathens. A product of the Danish 50cc school, he was also capped at U-21 level, and promised big things. He sounded every inch another Danish starlet, to follow in the footsteps of Gundersen, Nielsen, Knudsen and Pedersen of that era, and he made a very bright start to his Cradley career.
A string of good scores, with a little help, encouragement and team-riding from Erik Gundersen increased Jan's average from the assessed 6.00 with which he started. Unfortunately, despite the potential, the big man's performances gradually faded and he finished his one and only season with the Heathens on a sub-4.00 average. In 1988, he was not fitted into the team, and was instead replaced by another promising Dane by the name of Gert Handberg.