Mr Brooks is the Royal Beekeeper at Lancre Castle. He is one of those people whose occupation, like that of blacksmith is so old and arcane as to be tinged with witchcraft, and by tradition, has not so much a first name as a honorific. After all, most people, when thinking of bees and honey, are barely beyond the Magrat Garlick stage of asking "How do you milk them?", which means there is a lot of mystery to be exploited here for one in the know.
All the lore and mystery of working with bees is condensed into this one man, who offers Magrat Garlick a useful insight onto how she came to be Queen. Apparently all Queens start out as normal worker bee larvae, but for reasons unknown to Man, the other workers conspire to select one lucky larva and fatten her up with royal jelly until she becomes queen-elect. This, Magrat noted, was delivered with a suspiciously republican grin. If there is already a Queen in residence, the new Queen will elect to leave the hive with a small retinue of workers and drones, and set up her own hive somewhere else. (This echoes Nac Mac Feegle practice when a rare daughter comes to maturity and leaves to find a clan of her own).
Mr Brooks also mentions that sometimes events conspire, or the weather interferes, and two or more Queens will fight a duel to the death inside the hive. "the old Queen's more cunning and nastier, see? But the new Queen, well, she's got everything to fight for."
While Magrat cannot bear listening to this, she will come to recall this wisdom at a time when she has to fight another Queen for mastery of her own kingdom, and stab and slash for all she is worth.
Mr Brooks cannot abide wasps. He's seen how they can devastate a hive so as to get to the honey, and, he supposes, for fun. So when the Elves invade during Lords and Ladies, he loads a spray-gun with his most potent wasp-killer spray, and despatches several parasitical creatures.
It is possible that even Granny Weatherwax, a beekeeper herself, treats Mr Brooks with great respect, having in all probability learnt much from him.