Band's third album will be released in May
Mumford makes rare live appearance at Guildhall show
James Blake, Róisin Murphy and Ben Harper also added to bill
Faithless, Modest Mouse and Django Django also added to line-up
Band lead latest line-up additions alongside Royal Blood, Bastille and Catfish & The Bottlemen
The band will headline Bonnaroo festival in Tennessee alongside Billy Joel and Kendrick Lamar in June
The musicians recently released 'lost' Bob Dylan lyrics LP 'Lost On The River: The New Basement Tapes'
The band released their last album 'Babel' in 2012 and were thought to currently be on hiatus
Both bands appeared on the Gentlemen Of The Road stage in the Avalon Cafe
Johnny Flynn, Michael Kiwanuka and Nick Mulvey confirmed to appear