JAY-Z & RIHANNA RACK UP $11.5K BAR BILL

The "99 Problems" rapper and the "Umbrella" singer - who is signed to his record label Def Jam Recordings - partied with friends in the VIP lounge at London club Vendome, in the UK city's exclusive Chelsea district, on Tuesday night (July 21, 2009).

Jay-Z - who is married to "Crazy in Love" singer Beyonce Knowles - ensured their entourages enjoyed the evening by ordering countless bottles of expensive champagne and vodka.

A source said: "They had two of the VIP booths, so all of their people could mingle together."

"Jay–Z ordered countless bottles of Dom Perignon champagne along with vodka for both tables and the party really gathered pace."

"Everyone was trying to get into their area to get a glimpse of them but the security was so tight, many were left standing by the roped off area trying to sneak a peak."

"Rihanna, 21, partied until the early hours of Wednesday morning (July 22, 2009) and kept a low-profile when she left the nightspot."

The source added: "As she walked out of the VIP area she looked in high spirits. But she kept her head down as she made her way out of the club at 3am, avoiding questions from fans as to how she was doing."