Passage: Hamilton began karting in 1993, when he was eight, at the Rye House Kart Circuit and quickly began winning races and Cadet class championships. Two years later, he approached McLaren Formula One team boss Ron Dennis for an autograph, and told him, "Hi. I'm Lewis Hamilton. I won the British Championship and one day I want to be racing your cars." Dennis wrote in his autograph book, "Phone me in nine years, we'll sort something out then." Hamilton drove for Martin Hines's Zip Young Guns Karting Team. By the age of 12, his driving skill was high enough that Ladbrokes took a bet, at 40/1 odds, that Hamilton would win a Formula One Grand Prix race before the age of 23; another predicted, at 150/1 odds, that he would win the World Drivers' Championship before he was 25. He progressed through to Junior Yamaha in 1997, and in 1998, Dennis called Hamilton after he won an additional Super One series and his second British championship. Dennis delivered on his promise and signed Hamilton to the McLaren driver development program. This contract included an option of a future Formula One seat, which would eventually make Hamilton the youngest ever driver to secure a contract which later resulted in a Formula One drive.

Question: What did Dennis deliver on?
his promise