GreatFest is (as on their website):

“Our mission is to become the largest jailbreak/(i)community convention for coders, themers, hackers, developers or any other mobile device user. To leave others with the better understanding of what jailbreaking actually means to us, and that it does not stand for

piracy. We aim to build upon a community that we believe to be the
best there is. So please, tell the world our mission. MyGreatFest, for the community, by the community.”

The Conference starts at 9:00am GMT 17th Aug