Ted Hughes said he liked all of Philip Larkin’s poems (which was generous of him, considering the rubbishing he himself got from Larkin) and he liked him the more the sadder he got. I guess he may have particularly liked this one then, which has the core of desolation that one finds at the heart of so many Larkin poems, and expresses a sense of alienation and aloneness that strikes me as typically if by no means exclusively mid-twentieth century.
Talking in Bed
Talking in bed ought to be easiest,
Lying together there goes back so far,
An emblem of two people being honest.
Yet more and more time passes silently.
Outside, the wind’s incomplete unrest
Builds and disperses clouds about the sky,
And dark towns heap up on the horizon.
None of this cares for us. Nothing shows why
At this unique distance from isolation
It becomes still more difficult to find
Words at once true and kind,
Or not untrue and not unkind.
Philip Larkin
David Sutton 
I read a comment that the three-line stanzas hint at a third person in the relationship, who prevents the “two people being honest”.
Well, possibly – we know Larkin at certain periods of his life was invested in more than one relationship – but I think the poem can stand perfectly well without that biographical detail, though it would not be true of everyone of course: I’m sure that for many couples talking in bed is indeed easiest. Larkin is not necessarily the best guide to human relationships, any more than Hardy was, but then that’s not necessarily what we ask of a poet!
“At this unique distance from isolation” – at what should be this unique distance from isolation? The speaker is in a dark place but (as elsewhere in Larkin’s poetry) he has the consolation of finding tough, precise, startling words to describe the darkness?