LONDON, Nov 12 (Reuters) - Programming by Prince William and gritty dramas helped British broadcaster ITV rebuild its advertising base and predict growth in ad sales in the fourth quarter following a plunge earlier in the pandemic.

The channel, which will broadcast its ratings smash "I'm a Celebrity, Get Me Out Of Here" from Sunday, said advertising spend was down 7% in the third quarter, following a 43% plunge in the second quarter.

It is now forecast to grow in the fourth quarter compared with last year, with November up around 6% compared with the same period in 2019.

The group, Britain's biggest free-to-air commercial broadcaster, said the majority of its studio productions had also resumed but COVID restrictions and further lockdowns had increased the cost of operations.

"We are seeing encouraging signs in both our divisions," Chief Executive Carolyn McCall said on Thursday.

"Advertising trends are improving with Q4 forecast to be slightly up year on year and 85% of our productions in the UK and internationally that were paused as a result of COVID-19 are back in production or have been delivered." (Reporting by Paul Sandle and Kate Holton; editing by Guy Faulconbridge)