I'm a Celebrity... Get Me Out of Here opening overnight ratings
Series 1 (2002): 6.4m (33%)
Series 2 (2003): 10.0m (46%)
Series 3 (2004): 10.1m (n/a%)
Series 4 (2004): 9.0m (35%)
Series 5 (2005): 9.5m (38%)
Series 6 (2006): 8.9m (38%)
Series 7 (2007): 8.7m (38%)
Series 8 (2008): 8.9m (35%)
Series 9 (2009): 9.8m (36%)
Series 10 (2010): 11.2m (38%)
Series 11 (2011): 11.8m (44%) inc +1
Series 12 (2012): 10.6m (42%) inc +1
Series 13 (2013): 11.9m (47%) inc +1
I'm a Celebrity's opposition last year was 2.7m. War Horse is guaranteed to rate higher than that: it has a one hour head start and is bound to bring in an older demographic. I'd say around 4 million for War Horse.
With that in mind, I think we're looking at around 10.5m on Sunday for I'm a Celebrity. Last year's series was the most watched ever, and it would take the perfect storm to top that.
Although, as last year demonstrated, this is one show where predictions are utterly pointless.