The Cambridge Evening News article is here http://www.cambridge-news.co.uk/cn_news_cambridge/DisplayArticle.asp?ID=391245 apparently only two cars involved, although I would swear two cars had rammed each other plus the third one in the picture!
I would guess they were trying to do some high speed chase - the other two police cars were totally classic - rammed into the back of each other with some guys car tailgated into the back of them :-(