URGENT! Can I get a DATV visa at LHA

[debalina]

Hi All. I have a US H4 visa which has expired but i have valid extension documents(currently residing in US). I am going to INDIA from Boston via London for my visa stamping.
I don't have a DATV visa and now i don't have time to get one. Can I get a DATV directly from the airport. Please help!!