is it possible to meet my friend at the Heathrow airport ???

Dear users, i would like to know whether it is possible to meet my friend at the airport when he is travelling from one country to other country? my friend is living in USA and is going to India where his connecting flight is in London Heathrow. His departure is at Heathrow terminal3 (american Stupid) and arrival at Heathrow terminal5 (British Airways). halt for 6 hours and can i meet him at heathrow airport? what are the chances to meet him? do i need to take any ticket in general we can enter inside the airport but can we enter into the duty free area inside the terminal?

You cannot enter the duty free area if you're not travelling. However, if he's a non-visa national or has a valid visa, then he may be able to pass through immigration and come out and meet you.