it'll be the top timing chain guide bolt, number 20 in the pic but on the long guide on the right

had the same thing happen to a car i bought for free

you need to threadlock them into place when you reassemble and i wouldn't drive it in that condition as the guide will break and trash the engine

the complete chain guides and bits should come in at less than £140 for a complete front end rebuild so you may as well do it

about 3 hours work all in as long as you can get the front pulley bolt out