When Grimm insists to 21st Century London school boy, Jamie, that he was not only around but actually influencing events that involved Beowulf, Hengest and even King Arthur he explains that, as well as being an old man - he can be, a young man too.
After almost three years 21stC schoolboy Jamie meets up with Grimm again and this time Grimm finally tells Jamie the true story of King Arthur - well almost true, as true as his memory recalls, for he is no longer the young man, but the old man.