Gregor Van Baalen was a member of the salvage company, Van Baalen Bros.
When the captain of the Van Baalen Bros.' salvage ship, Tricky Van Baalen, was in an accident that lost him his sight, voice and memory, his brothers, Gregor and Bram, decided that it would be funny to make Tricky think he was an android. As a result, Tricky was no longer in command and Bram and Gregor became "equal partners".
When the brothers came across the Doctor's TARDIS, they used their magno-grab to haul it in as salvage, causing damage to its engines and fuel to leak. The Eleventh Doctor, having been thrown free from the TARDIS convinced the Van Baalen Bros. to enter the TARDIS under the promise of the "salvage of a lifetime." Once on board, the Doctor locked the doors, trapping the brothers inside the TARDIS and forcing them to help find Clara under the pretence of the TARDIS' fictitious self destruct sequence.
While searching for Clara, Gregor stole a piece of the TARDIS' architectural reconfiguration system, causing the TARDIS to create loops, labyrinths, and echoes of itself. When Clara was rescued and the countdown was stopped, the Doctor realised that the TARDIS' engines were set to explode due to the damage from the magno-grab's field.
When the TARDIS' fuel rods began to break apart and trapped Tricky, Gregor was forced to tell him the truth about what happened to him before freeing him. As they reached the Eye of Harmony, Tricky pushed a zombie of one of the group's future self, and almost fell off the walkway. The Doctor warned them not to touch lest time reasserted itself, but Gregor pulled Tricky to safety, and they fused, taking on the form of one of the zombies.
This timeline was undone by the Doctor. In the new timeline, the TARDIS briefly appeared on the salvage ship's monitors before quickly vanishing before it could be pulled in by the magno-grab field. In this timeline, a photograph of the three brothers and their father remained intact (it had previously been torn to omit Tricky as part of his brothers' ruse), and Gregor treated Tricky with more respect. (TV: Journey to the Centre of the TARDIS)