During periods of low complexity traffic, it’s wasn’t (historically) uncommon for Enroute controllers to agree to send specific flights, or indeed specific or even multiple flows of traffic, on direct routes to to certain points with the aim of reducing track mileage, saving flight time and fuel etc. GMH was a key point to send eastbound traffic ex-UK from around Manchester and the north to, and typically for (IIRC) destinations such as Munich, Frankfurt and overflights. There were other points used for other destinations too and, likewise, points were offered to Maastricht etc to send traffic westbound into the UK.
This was fairly common in the nineties and early naughties (I must have sent thousands there in my time) but, progressively, airspace redesign has obviated the need in many cases with routes much straighter these days, and will all but be a thing of the past with Free Route Airspace more widely deployed across Europe.