At the majority of airports I fly out, there are basic tugs used to push the airliners back. They are hooked on using a towbar and push the jet out. The tugs at Heathrow are a bit different from the ones I am used to seeing. They are the type of tug that actually picks up the noseleg to move the aircraft out. The leg is surrounded by the tug and elevated. The tug then drives wherever required with the leg coming along. They are pretty substantial beasts. Moving a widebody needs a big tug I guess. They can move a 747 or an A380 but in this case “only” a 787.