The British comic made the most of the snow that's causing havoc across the country to take his pop star love sledging on a steep hill in Hampstead Heath, near Russell's home.
And by the excited look on Katy's face, she loved every minute.
The couple, who have been dating since September, later took a romantic walk around the park. And in the evening they went to see a carol service at St Paul's Cathedral followed by a trip to the theatre to see The Lion King.
Russell seems keen to cram in as much as possible while 25-year-old Katy is on his home turf. He has also taken her to see his favourite football team West Ham and on a shopping trip.
For her part Katy is having the time of her life, though she seems to be struggling with the differences between UK English and American English.
She wrote on Twitter: “Chips/crisps. Trash/ bin. Trunk/boot. Bathroom/loo. Zebra/Zahbra. Vitamins/Vitaminz. Lady bug/Lady bird. I need English lessons.”