Arrival to Heathrow Airport (airports, international flights, crowded, time)

[Maple47]

British Airways advised I have to be at the airport 4 hours prior to departure.
Heathrow website advised: 3 hours.
My flight is at 10:30 AM.
What is the common practice? Four hours sounds somewhat strange...

[beachmouse]

Unless you're headed to Israel (enhanced screening ahoy!) three hours is fine.

[MB1562]

3 hours for international flights at major airports.

2 hours for domestic flights.

I've used this rule every time I've flown and it's never failed me, even at major, crowded airports like Heathrow.