Former Children's Laureate Michael Rosen is "very poorly at the moment” and spent a night in intensive care, his family have said.
The statement on Twitter said he was "now doing OK" and was "stable" and "alert" having been moved to a ward on Sunday.
It is not known whether the 73-year-old's condition is related to the coronavirus.
The children's novelist and poet was Children's Laureate from 2007 to 2009.
His many works for children include We're Going on a Bear Hunt, Little Rabbit Foo Foo and Tiny Little Fly.
Cressida Cowell, author of the How to Train Your Dragon series, said she hoped he would "recover swiftly".
Rosen's family thanked all his Twitter followers "for all their kind concern".