"My magic is dead"

I don't know who wrote this poem, except that it wasn't me, or where it came from, other than the UK before 1971 and presumably after 1969, but it's been stuck in my head today.

Update: areia points out a reference in an article which implies that this is "The Witch's Cat", by Ian Serraillier. Thank you!

"My magic is dead," said the witch. "I'm astounded
that people can fly to the moon, and around it.
It used to be mine and the cat's, till they found it.
My broomstick is draughty, I snivel with cold
as I ride to the stars, I am painfully old,
and so is my cat.
But planet or space-ship, rocket or race-ship
never shall part me from that."

She wrote an advertisement. "Witch in a fix
willing to part with the whole bag of tricks,
going cheap at the price of eighteen and six."
But no-one was ready to empty his coffers
for out-of-date rubbish. There weren't any offers,
except for the cat.
"But planet or space-ship, rocket or race-ship,
never shall part me from that."

The tears trickled fast, not a sentence she spoke
as she stamped on her broom and the brittle stick broke,
and she dumped in a dustbin her hat and her cloak,
then clean disappeared, leaving no prints,
and no-one at all has set eyes on her since—
or her tired old cat.
"But planet or space-ship, rocket or race-ship,
never shall part me from that."

I swear we live in a sitcom

Rio: But I thought when people said "trinity" they meant "faith, hope and charity".
Marn: Well, the Latin word "trinitas" means "three-ness", so anything there's three of can be a trinity.
Rio: Like our cats.
Marn: Right.
Rio: So what are faith, hope and charity?
Marn: Theological virtues. But when people say "trinity" they usually mean the three persons of God. I mean, in Cambridge there's a church called Holy Trinity, but it's named after God, not faith, hope and charity.
Rio: Right, and it's not as if there's a church named after our cats.
Marn: True. ...Although there is the Rothko Chapel.