As for little Imogen, she said, 'Oh, my!' and kept her mouth very much open indeed.
'Where are we ?' Cyril asked the Psammead.
'In Britain,' said the Psammead.
'But when ?' asked Anthea anxiously.
'About the year fifty-five before the year you reckon time from,' said the Psammead crossly.

'Is there anything else you want to know ?' it added, sticking its head out of the bag formed by Anthea's blue linen frock, and turning its snail's eyes to right and left.

'I've been here before--it's very little changed.' 'Yes, but why here ?' asked Anthea.
'Your inconsiderate friend,' the Psammead replied, 'wished to find some home where they would be glad to have that unattractive and immature female human being whom you have picked up--gracious knows how.

In Megatherium days properly brought-up children didn't talk to shabby strangers in parks.

Your thoughtless friend wanted a place where someone would be glad to have this undesirable stranger.