Air Travails 2: Do I Need a Transit Visa in UK

As I was shopping online for airfares from Washington area to Delhi on Oct-2, I came across this incredible price of $569 return fare on British Airways (via Travelocity). Normally any price below a thousand bucks is considered a deal. So, as I was drooling over that price (the site said only 3 seats were left at that price), I considered if I needed a transit visa if I bought this itinerary that transited through London Heathrow.