Batty
Im going to give this a try, Im not a controller but a pilot who spends to much time with atc simulators.
If Im not totally wrong the London TMA sector BNN (119.77) "ownes" from FL195, while S27 (130.92 i think) ownes down to FL195. Airplanes on Lorel arrival will leave sector 27 through its vertical boundary. Now to meet the CLIPY restriction airplanes need to enter BNN sector in good time for controller to be able to accomodate its further descent. So therefore a ROGBI is inserted in the arrival for S27 to be able to transfer airplanes on to BNN.
Now, this is just my guess, but I hope its correct.
Cheers / Duece
Edit: My brain is like a mushroom after the weekend