car wont start ford focus tdci 1.8?

went on holiday friend turned the engine over for me once then a few days later tried again but the car wouldn't start,flat battery,on my return home i put on a new battery i can get into the car okay with both my keys the central locking works,but i cannot start the car all the lights,radio air con work but the engine won't start the small light above the clock flickers for about a minute then flashes randomly and engine won't start