The firm said the Grand National results, which came after the end of its first quarter, even surpassed its record win on the 2009 race when Mon Mome romped home at 100-1.
Bookmaker William Hill hailed a "successful" start to 2013 after enjoying its best ever result at this year's Grand National when 66-1 outsider Auroras Encore won at Aintree.
William Hill said it saw a poor Cheltenham festival last month, although this was offset by good football results after the Champions League saw no English teams in the quarter final for the first time since 1996, as well as a lucrative Six Nations, when Wales beat England in a crucial finale.
The group reported an 8% jump in earnings in the first three months of 2013 after net revenues rose 15%, with its online operations the star performing division once more.
Sporting bets made online were higher than that spent "over the counter" in its high street betting shops throughout the first quarter, with increasing numbers of bets made through its mobile apps.
It said its app was downloaded 45,000 times on Grand National day and 51,000 times during the Cheltenham Festival.
William Hill's figures have left Ladbrokes trailing behind after its rival warned earlier this week that annual profits would be at the bottom end of City forecasts following a difficult quarter.
Ladbrokes reported a £13 million drop in profits to £37.4 million in the three months to March 31, including £6 million in lost revenues after a good week for punters at Cheltenham.
William Hill has been reaping the benefits of a burgeoning internet offering, with first quarter online revenues up by more than a fifth in the first three months of the year and earnings up 13%. Mobile sportsbook bets jumped 145% higher. This helped offset a 3% fall in earnings across its 2,400 betting shops.
Ralph Topping, chief executive of William Hill, said: "Having grown our UK online market share from 10% to 15% over the last four years, we aim to increase our share and are making significant investments in marketing, technology and people to achieve that."