In the last episodes of David Tennants final days of being The Doctor, the storyline traces the life of Donna Noble after The Doctor removed her part-Time Lord and all her memories of her time with him.
Her post-Doctor life see her meet a very unextraordinary man and we hear of their money struggles. In the final scenes, the Doctor turns up at Donna's real wedding - where she can only afford a cheap tiara - and gives her mum a wedding present of a lottery ticket.
The Doctor knows his days are numbered, so bends the rules, we guess to deliver winning lottery ticket-to-be. That's the best gift he can give Donna under the circumstances. Donna will never need discount tiaras again.
