Estimate, the racehorse which has tested positive for a banned substance, helped make sporting history for the Queen as she became the first reigning monarch to win Royal Ascot's Gold Cup.
The Queen was pictured beaming as Estimate crossed the line in first place during the dramatic race last year.
Prime Minister David Cameron congratulated the Queen in a tweet saying: ''Huge congratulations to Her Majesty for Estimate's victory at Royal Ascot - first time ever a reigning monarch's horse has won the Gold Cup.''
Her Majesty won £155,960 in prize money after Estimate's victory.
More top news
A further 85 buses are expected to arrive on Tuesday and Wednesday, with officials saying the entire operation will last at least a week.
The reality star had filed a defamation lawsuit against celebrity gossip site MediaTakeOut.com.
The model and reality TV star said she had "never been so scared in my life" after finding Shavaughn McKenzie lurking in her driveway.