I'll be in London for a week and strongly considering a 3 day trip to Prague. My plane arrives at LHR @ 6:25 am. There's an EasyJet flight leaving out of Gatwick @ 8:55 am the same day at a very good price. Considering the size of Heathrow, possibilities of delays, and the distance from Gatwick would it be unreasonable to think I could make this?

"... would it be unreasonable..."

Very unreasonable, doomed to failure.

I think it would be delusional to think you could make it, even with no delays. Size of LHR is irrelevant but the traffic from LHR to LGW on the M25 in the rush hour (unless you are travelling on a Sunday) will mean you need at least 3.5 hours to make the connection. Getting through security at LGW in peak travelling time can also take a long while. Why can't you fly from LHR to Prague, any cost saving by going to LGW potentially be eaten up by this transfer.

Forget it. AA once told me to allow at least four hours. I have done it in less, but not in rush hour, and I certainly wouldn't plan on it.

Also, size of the airport is less important than the size of the queue at passport control.

thanks for your feedback. this particular idea has been wiped off the face of the earth

I completely agree with thursdaysd and michelhuebeli. Sorry that your idea did not work as you wanted. But the reality is that the queue at passport control would be really long... and no matter how strongly you will rush you will have to wait about an hour or even more. However, wish a good flight and unforgetable experience

I wouldn't try to go LGA to JFK, I'm certainly not going to attempt an LHR-LGW connection.

LHR-LGW is not difficult - you just take the National Express coach. But you do have to leave enough time.

exactly, I've done that connection, it wasn't difficult just takes time