The library mice have their own way of celebrating birthdays. For the 30th, they celebrated with crumbs from the children’s party and a chunk of cocktail cheese.

For the 50th, the few cupcakes had been eaten and every crumb swept away and there was no after work party because of cutbacks.

But one of the mice noticed a child’s drawing of a mouse balancing books and wishing the library a Happy 50th Birthday.

‘That’s how we should celebrate,’ it said.

‘Let’s find ALL the books with fifty in the title,’ suggested another mouse.

They headed for the large James Patterson section.

‘I’m sure I saw one here once,’ said the mouse. ‘It was called Fifty-Fifty.’

Another, very squeaky mouse asked, ‘What about E. L. James?’

Nobody was listening. She ran off.

Meanwhile, a mouse with a more authoritative voice called the others over to the returns trolley. A cheese-coloured cover had caught her eye. The book was called The Periodic Table: A Field Guide to the Elements.

If you’d seen how quickly they pushed it onto the floor, you might have thought it really was a field guide to cheese. The chemistry book fell open at a page that said:

‘Sodium – Atomic Number 11. Special Trick: Reacts violently with water.’

‘I don’t like that.’

They turned the page.

‘Magnesium – Atomic Number 12. Special Trick: Burns with a brilliant white flame.’

‘Oh dear! Oh dear!’

Their little hearts beating faster, they turned the pages until they found what they had been looking for.

‘Tin – Atomic Number 50. Special Trick: Good for holding food.’

‘Perfect!’ they said as one.

They left the book where it lay and ran past the very squeaky mouse, who was still staring at the spine of GREY – the only E. L. James title on the shelves.

The mice disappeared through the secret tunnel to Poundland. Being library mice, they knew how to open tins and hide the evidence. The spaghetti in cheese sauce went down well, but the tinned sponge pudding was even better.

They agreed it made a thoroughly satisfying ending.