While Alistair doesn't atually make an appearance in any of the books (having died when Wartrop was somewhere in his early twenties) he plays a significant role in the fisrt book. Having brought the main antagonists (the Antropophagi) to New Jerusalem.
As stated in the first and second book Alistair was a Monstrumologist, like Wartrop and was probably the reason Watrop took up the profession.
Bringing in the Anthropophagus
As stated before Alistair is resposible for the appearance of the Antropophagi in New Jerusalem, having commisioned a Captain Varner sometime in late '63 or early '64 to go to Benin and retrieve four of the flesh eating monsters from the residing Oba of the island.
Once the ship, Feronica, reached land Wartrop assumably tranported the Antropophagi to an underground feeding hole that was hidden inside of the Wartrop Family Crypt. He then enlisted Dr Starr as to the feeding of the monsters, since the doctor had a supply of human 'fodder' at the ready, namely the poor accupants of Starr's asylum.
Warthrop Senior died in the guest bedroom by natural causes after destroying all evidence of his existence, including the clothes on his back. The only thing of his that survived after he died was a trunk found under the basement stairs. Pellinore assumed that he had forgotten about it.
The trunk contained two significant items to the investigation of Anthropophagi, a journal and a shrunken head in which Will Henry finds a key.
Pellinore described his father as being neat to the point of fastidiousness about his appearance and surroundings. (Which also brings hint of confusion to his death since he died naked as the day he was born.) He was a proud man that submerged himself in his work and had little time for his son.