The poem
Once I believed in you, And then you came, Unquestionably new, as fame Had said you were. But that was long ago.
You launched no argument, Yet I obeyed, Straightaway, the instrument you played Distant Down sidestreets, keeping different time,
And never questioned what You fascinate In me; if good or not, the state You pressed towards. There was no need to know.
Grave pristine absolutes Walked in my mind: So that I was not mute, or blind, As years before or since. My only crime
Was holding you too dear. Was that the cause You daily came less near—a pause Longer than life, if you decide it so?

I'm sorry, but the very first thing that popped into my mind as I was reading this was the sad situation of Christie Brinkley's husband. Imagine--him being a 47 year old man messing with a young (18) teen that worked at Toys R Us. Um...
The spirit of---??wooed the man in the poem. The spirit is defined in the poem, which Larkin leaves for the reader to discover and draw their own conclusions. The spirit left the man without common sense, and much regret. It was bewitching, and left destruction.
The Spirit Wooed
Some bimbo in Toys are Us, I don't think so. More likely the Spirit of Jesus, I think