Emma Thompson has swelled the ranks of Warner Bros' ensemblecast on Harry Potter And The Prisoner Of Azkaban after signing on to playthe eccentric professor of divination Sybll Trelawney.

Thompson joins Daniel Radcliffe, Emma Watson, Rupert Grint,Maggie Smith, Robbie Coltrane, Alan Rickman, Gary Oldman, David Thewlis andMichael Gambon - who stepped into the role of Hogwarts headmaster ProfessorDumbledore following the death of Richard Harris.

"I am very excited to work with Emma," Alfonso Cuaron, thefilm's director, said in a statement. "She brings such life and spirit to thecharacters she portrays. It will be exciting to see her as Trelawney."

The in-production Harry Potter and the Prisoner ofAzkaban is the third adaptation in author J K Rowling's smash-hit bookfranchise, in which Harry must confront the enigmatic escaped prisoner SiriusBlack

The film is due to open worldwide in summer 2004.