In a post on Instagram, Hannigan said: ‘This cut is so deep I fear it can never heal.’

The English actor was best known as librarian Rupert Giles in the cult US supernatural TV series.

US actor Brendon has died in his sleep of ‘natural causes’.

The 48-year old was due to return as Buffy Summers in a new Hulu show but it was announced last week that it was no longer going ahead.

Trachtenberg’s death at 39 is not being treated as suspicious and police said a medical examiner will determine the cause of her death.

Trachtenberg played Georgina Sparks on the show.