The domestic stock markets witnessed their biggest post-Budget Day rally ever, today, while the rupee also notched up very strong gains against the dollar. A day after the presentation of the Union Budget, the Sensex at the Bombay Stock Exchange gained a phenomenal 777 points, to close at 23,779, on across-the-board buying by investors. This is the biggest single-day gain of the Sensex in nearly 7 years. The Nifty at the National Stock zoomed 235 points, or 3.4 percent, to 7,222. We asked market expert, Avinsah Gorak Shakar what was behind the stupendous market surge. The rupee also rallied very strongly, posting this year's biggest single day gain of 57 paise, to 67.85 against the dollar.