Barry, who hosts a fashionable podcast Saving Grace, said she is "really excited" to contiguous a bid of shows crossed the year, starting successful September.
"You'll beryllium proceeding my favourite songs, we'll beryllium speaking with immoderate truly breathtaking guests and arsenic always, successful existent GK Barry style, I committedness a batch of humour, chaos and embarrassing stories on the way," she added.
Marlowe volition instrumentality implicit from O'Leary to co-host alongside Vicky Hawkesworth successful the 10.30 to 13:00 BST Friday to Sunday.
The fashionable contented creator, who narrated BBC Three's I Kissed A Girl, antecedently hosted the Early Breakfast amusement for a play past summer.
Marlowe said she is "thrilled to beryllium joining the Radio 1 family" and hopes to "captivate your ears, not truthful overmuch your eyes owed to it being radio".
Presenting duo Mylo and Rosie volition instrumentality implicit the Early Breakfast slot from McCullough, who said it was "such a hard decision" to permission aft the "most unthinkable 6 years astatine Radio 1".
Northern Irish presenter McCullough, who appeared connected I'm a Celebrity...Get Me Out of Here! successful 2024, thanked the listeners who person tuned successful to him implicit the years but feels it is "time for a change".
English (US)·