"Lunch with Professor M." was a favourite fake appointment, as was "MP in Brandenburg", the court in Hannover heard from Wulff's former secretary, the Welt newspaper reported on Wednesday.
“When we needed a weekend off we wrote ‘MP in Brandenburg’," the woman said. Wulff was state premier (Ministerpräsident in German) of Lower Saxony between 2003 and 2010 - and then Federal President from July 2010 until February 2012.
He is on trial accused of accepting favours while in office in Lower Saxony. His friend film financier David Groenewold is said to have paid more than €700 for part of Wulff's stay at a posh hotel in Munich during the 2008 Oktoberfest.
In return, it is alleged, Wulff returned the favour by urging Siemens boss Peter Löscher to fund a Groenewold film project. But Wulff claims he backed the film because it was on a topic close to his heart.
He told the court on Wednesday he had barely had time for his personal life while state premier - contrary to what he said was the common view.
“People have the impression that I spend most of my life on [the Baltic island of] Sylt and [the Italian island of] Capri,” he complained.
Groenewold's former secretary also gave evidence, saying she had assumed Wulff was her boss’s guest when she booked a suite for the two men in the luxurious Munich hotel Bayerischer Hof.
Who eventually footed the bill she didn’t know, she said. The secretary told the court: “What the gentlemen agreed upon there was not my concern.”
Compared to political scandals elsewhere, the charges Wulff faces may seem trifling. Many commentators, however, say the trial proves that no public official stands above the law.
If found guilty, the former largely ceremonial head of state could theoretically face up to three years in jail or a fine. A verdict is expected some time next year.