Hobbs, known as a champion of new dance music, left her Thursday 2am-4am show earlier this year to take up a position at the University of Sheffield.
Benji B, who has presented a weekly show on 1Xtra since it launched eight years ago, will leave the digital station on Sunday October 10, to make his Radio 1 debut four days later. He says the move will bring the essence of his 1Xtra show to Radio 1.
The move means there will be a new Sunday night line up on 1Xtra, with Target's 100% Homegrown show (currently on Sundays, 7pm-10pm) moving to 10pm-1am. From 7pm - 8pm there will be a new show, My Top Ten, in which 1Xtra playlisted artists play their favourite ten tunes each week; from 8pm-9pm there will be an hour showcasing the best of 1Xtra's shows from that week; and 9pm-10pm becomes the new home for documentary strand BBC Radio 1Xtra's Stories.
Radio 1 deputy controller Ben Cooper says, "Benji B's reputation for finding and supporting new cutting edge music is exemplary, and I'm excited about him being able to put his own mark on the slot by bringing some of the finest cutting edge dub step and experimental electronica to our audiences."