At about 10:30/10:40pm on Saturday 30th April 2011, I witnessed 2 formations of lights that moved in a westerly formation, within the middle of the city of Norwich, United Kingdom.As I was walking along King St heading in the direction of The Waterfront (a club next to the River Wensum) with friends, heading in a South-westerly direction, I looked up and saw 9 lights heading west at rapid speed in 2 separate groups. The night sky was hazey, and it was hard to make out even the brightest stars, such as Venus or Polaris. There was 2 distinct formations, one consisting of 3 lights, and a larger group, which had five but was joined by a sixth, that was further north than the smaller group and was of similar appearence in colour, both of which headed in a Westerly direction, out towards the North Sea, over the Norfolk Broads. The light that joined the larger group, performed a sharp right turn, about 30 degrees turn, to formate with the larger group. All the lights appeared Whiteish Amber in appearence. Due to distance, I was unable to tell what the lights were.The smaller group, which appeared more southerly out of the 2, appeared in a V formation, with one lead light leading, and the other 2 behind and to the left and right, similar to a Vic formation used by pilots. The larger, more northerly group, originally had 5 lights, in a pyramid-looking formation, with a lead light, then 2 behind on the left and right, and then 2 behind them with one on the outher left and another to the right of that but in the middle. A sixth light headed towards this group and turned sharply in an un-natural fashion to take a place in the back of the group, on the right hand point of the pyramid. As Norfolk is over-flown by both US Air force and Royal Airforce fighter jets, the turn performed by light to join with the formation was aggressive, and a distinct change of direction as opposed to a gradual turn that would be made by military jets (I have witnessed Eurofighter Typhoon and Boeing F-15 Eagle Fighter planes perform DACT (Disimilar Air Combet Maneuvering) in the skys in both day and night). The 2 formations headed in a Westerly direction, over the Broads and out to the North Sea. The event lasted for about 15 seconds as the lights deminished rapidly. When I alerted my friends to what I witnessed, no one had looked up and spotted the lights. and as I tried to direct their view to where I has seen the lights, no one was able to see any lightsAs an Aviation Enthusiast (or plane spotter to put it in Laymans terms), I can tell between Military ,Commercial, and Civilian aircraft at day and night. On a Saturday, it is very rare to have Military jets flying, let alone at night and over a major UK city. Flying operations out of Norwich Airport would have stopped by that time of night and although Comercial airliners fly over Norfolk, none would fly in formation, let alone join up with a group of planes at night. Although I have no way of knowing what these lights belonged to, whether they be fighter jets, airliners, privately owned planes, or something not of this earth like a Meteor os space debris re-entering the Atmosphere, I do know that these lights are unidentifiable and beyond my knowledge of aviation. I can only hope that my sighting may have been witnessed by others in the Norfolk area. Thank you for your time and patience with my sighting.