Prince William 'Ditches' Pregnant Kate Middleton For Bachelor Party and Night Out (PHOTOS)

Although Prince William has shared he's very excited to become a new father, he's also revealed he isn't looking forward to the sleepless nights with his newborn baby; the usually conservative royal was recently photographed out in London with his brother Prince Harry, where the two reportedly partied it up on Saturday night, according to Entertainmentwise.

The Duke of Cambridge kept it casual for his night out on Saturday, sporting dark jeans, a black sweater over a blue dress shirt and an orange baseball cap that partially hid his face from paparazzi.

Prince William and Prince Harry were at a bachelor (or "stag") party for their friend Thomas Van Straubenzee, who is due to get married later this year, and reportedly had been drinking all day in celebration of the impending end to his bachelorhood.

The brothers joined him and friends at the Chelsea club, and according to onlookers, Prince William was far more rowdy than usual on the dancefloor at the club owned by his close friend, Guy Pelly.

"William was really going for it. He was dancing loads and singing along to the music. He kept on waving his hands in the air and was shouting," an eye-witness told The Sun.

The brothers allegedly downed large cocktails and danced along to the "Harlem Shake," while Prince William spent time in the VIP area "close to girls dressed in just swimwear."

"At one point he even banged along to the music on the low ceiling," one onlooker told The Sun. "There were about ten of them. They looked like they were having a great time."

Earlier in the day, the brothers were spotted celebrating with friends at Kew Pier on the Thames, and one Twitter user who spotted the posh party wrote: "Prince William and Prince Harry aboard a proper rah stag do at Kew Pier. Hilarious," according to The Sun.

"All the mothers have been looking at me, 'just you wait, just you wait. Long sleepless nights'," Prince William said at the opening of a Help for Heroes recovery center recently, though he's said he is looking forward to becoming a father for the first time, as his wife Kate Middleton is scheduled to give birth July 13.

Click here to see photos of Prince William and Prince Harry following their wild night out on the town.