Query

I have just lost an on-line 3 day move game that in the end responded like I was playing a computer - the instant I pushed the submit button the opposition responded, the intervening time was nil - too fast for a human consideration and response - Is this possible, if so I'm out!

Your opponent made a conditional move. So they anticipated your next move and put the condition in that if you made that move, it would automatically play a response.  These are often used to make a turn-based game go a little faster, especially when you anticipate next move. To be clear, the move that they instantly responded with was their choice and not any computer or engine.

For more information regarding conditional moves: 

https://support.chess.com/customer/portal/articles/1444845-what-are-conditional-moves-

winmarleigh , a tip dont be flustered by conditional moves , always devote the time you need to your move consideration even if that is 3 days

Thanks for that ANOK1 - appreciated.

Difference between these two