won't settle in bed

[F1rstt1meGranny]

2-year-old grandson, who has always slept well till now, took to toddler bed brilliantly, but now, some 5 weeks on, gets very distressed at bed time. No change in pre-bed routine, but suddenly unhappy little boy. Very distressing for all. Any ideas welcome.

Sometimes they can become afraid of the dark as they develop their imaginations - is he better if you leave the light on outside the door?