Twitter's impact on journalism, Mail on Sunday editor Geordie Greig, Ashley Highfield of Johnston Press

Twitter is ten years old and has had an "utterly transformative" impact on journalism. That's according to Emily Bell, Director of the Tow Centre for Digital Journalism at the Columbia Journalism School. She says it has been the most important journalistic tool since the phone. We'll hear from her and from radio and TV presenter Richard Bacon, one of the UK's pioneers in using Twitter. He has 1.5 million followers and has experienced both the bright and very dark sides of Twitter.We'll also ask if we - all of us - are too quick to share pictures and video on Twitter and other social media in the aftermath of terror attacks, like those in Brussels yesterday? We'll be hearing from Hend Amry who began #ISISMediaBlackout on Twitter to discourage users from sharing ISIS propaganda online. She feels that sharing footage of attacks inadvertently serves the purpose of terror groups who hope to spread panic.Also - the editor of the Mail on Sunday, Geordie Greig, will reveal what he thinks helped his newspaper to win Newspaper of Year at last night's Society of Editors Press Awards.And the Chief Executive Officer of Johnston Press, Ashley Highfield, will discuss his plans for the i newspaper, which the Johnston Press is in the process of buying. How will the i thrive without the content previously supplied by the Independent newspaper? And with so many local newspapers in the Johnston Press empire now labelled "non-core" or "sub-core", will their future be blighted by cuts, strikes and closures? All questions for Ashley Highfield.