Its Episode 2 of the Charity Gunging:

So I finished off Pippa with a squirt or two of salad cream and then turned on Jess. She had been laughing at Pippa as she was being gunged but now it was her turn she tried to get away..... not so fast, I used pies, custard, gunge, spaghetti, black treacle and flour leaving Jess totally trashed and her uniform in tatters!

Good Job though I say it myself

Charity Gunging Pt 2 - Messy Angel

Fantastic pics of Pippa and Jess, Miss T!