He applied for a government grant, but was turned down, and after being ridiculed for his ideas, dropped out of the public eye and began secretly working on a machine that could manipulate time.
Whitaker later worked with Sir Charles Grover on Operation Golden Age. Working with his assistant, Butler, he brought various dinosaurs forward in time to clear present day London of its inhabitants as part of the scheme.
A peasant from the Middle Ages was also brought forward in time at one point, but it remains unclear as to whether his appearance was a mistake or an early experiment by Whitaker. Whatever the case, the peasant was taken back to his own time by the time eddy shortly after.
Whitaker gave Mike Yates a device to sabotage the Third Doctor's stun gun to prevent him from capturing a dinosaur and learning too much about what was going on. Whitaker materialised a Tyrannosaurus rex by the Doctor in the hopes it would kill him, but the dinosaur was knocked out by Yates.
While preparing for the final countdown, their plans were exposed by the Doctor. Grover tried activating the machine, but unbeknownst to him, the Doctor had disabled it by reversing the polarity. Whitaker, knowing this, tried to stop Grover, but it was activated and sent both of them to an unknown point in the past. (TV: Invasion of the Dinosaurs)