Music and reality TV mogul Simon Cowell left his pregnant girlfriend Lauren Silverman at home on Monday (07Oct13) as he celebrated his 54th birthday with his ex Terri Seymour and a group of pals. The X Factor boss, who will become a first-time father early next year (14), enjoyed a night out at West Hollywood hotspot Sur and was joined by his fellow former American Idol judge Randy Jackson and TV presenter Seymour as he marked his big day. As the party left the venue in a waiting car, Seymour was photographed appearing to sit on the birthday boy's lap to make room for another friend, with Cowell leaning back and covering his eyes. Seymour and Cowell dated for six years until 2008 and have remained close. Meanwhile, Cowell's birthday started with a big clean up - his new girl group Fifth Harmony wished the mogul a happy birthday by attacking his house with toilet paper. They also surprised him by hanging up a huge banner which read: 'Happy 87th Birthday Simon!'.