Gandalf as Sherlock Holmes has grown grotesquely old, with bloodhound jowls and liver spots and wrinkles. He is sagging into the earth. One heartbreaking scene features the distant cliffs of Dover searing into sharp relief, behind Sir Ian McKellen's long-retired, nonagenarian detective. Was I over-thinking it, or did this symbolise not only the war that Britain had recently survived, but also the lifelong battle that Sherlock had won with himself? I can't say more without spoiling it. Go, see.
We all know that Sherlock's not real; and yet that he is as non-fictional as a novelist's invention can be. I didn't race to see it because I feared what it might make me hear about ageing. Because we're buggered and going down, and I'm not in any rush. After you.
But there is hope. Though I felt every creak of his knees, every gasp for oxygen, every un-shed tear and pang of longing, I blinked back into the light with a fierce awareness that being old is nowhere near as wretched as it is cracked up to be; as those so terrified of it that they butcher their tits and faces want us to believe.
We do know, because we were there, that being young wasn't all that. Drop-dead gorgeous 24/7, were you? Nor me.
Our state of mind reflects the state of our lives at any given moment. Pause for thought. When was it that the primary synonyms for 'happiness' became 'money', 'beauty' and 'fame'? Other cultures revere and defer to their elders. Ageing, in ours, is about invisibility. Embarrassment. Decline. 
Sherlock's message in this wrenching piece is simple. There is not much to fear. We will always be exactly who we are now. Just older. We will always be who we always were, within. We still rage, though we age. With the piling years, the unfathomable becomes clearer. It dawns on us, as it dawns on old Sherlock, that we've got to fix stuff. We must do so with haste and vigour, aware of the hourglass's emptying, of the closing of the circle, of the need to make amends. We must do right by those wronged. We must avoid, in the wherever beyond, the hell of regret.