Shocking footage shows the moment panicked schoolchildren fled for their lives after a gang of youths crashed a school birthday party and launched a horrifying knife attack. Dozens of police officers swooped on Elm Park Primary School's hall, in Havering, Essex, at around 9pm on Saturday when a group of more than 50 youths armed with knives and machetes reportedly gatecrashed the 16th birthday celebration. The fighting, which police say involved a 'number of teenagers', allegedly lasted until 11pm, with two victims, aged 16 and 19, taken to hospital with non-life threatening knife injuries. Police said three teenagers were arrested...