transit: in transit through London Heathrow, night stopover, Indian citizen with US visa. UU

I am an Indian citizen who travels from India to the United States through London. I have a 19-hour stopover during the night in London. According to the official website, I do not need a transit visa since I have a confirmed ticket for the trip and a US visa. However, it seems that in spite of that it is still uncertain and depends on the official visa. Does anyone have a similar experience?