dst = GetPrevVehicleInChain(dst);

			/* Now if the vehicle we want to link to is the vehicle itself, drop out */

			if (dst == src) return CMD_ERROR;

			// if dst is NULL, it means that dst got a rear multiheaded engine as first engine. We can't use that

			if (dst == NULL) return CMD_ERROR;

		} else {

			/* there are more units on this train, so we will add the wagon after the next one*/

			dst = dst->next;

		}

	}

	if (IsTrainEngine(src) && dst_head != NULL) {

		/* we need to make sure that we didn't place it between a pair of multiheaded engines */

		Vehicle *u, *engine = NULL;

		for(u = dst_head; u != NULL; u = u->next) {

			if (IsTrainEngine(u) && IsMultiheaded(u) && u->u.rail.other_multiheaded_part != NULL) {

				engine = u;

			}

				if (engine != NULL && engine->u.rail.other_multiheaded_part == u) {

					engine = NULL;

				}

				if (u == dst) {

					if (engine != NULL) {

					dst = engine->u.rail.other_multiheaded_part;

					}

					break;

				}

		}

	}

	if (IsMultiheaded(src) && !IsTrainEngine(src)) return_cmd_error(STR_REAR_ENGINE_FOLLOW_FRONT_ERROR);

	{

		int r, num = 0;

		r = CheckTrainStoppedInDepot(src_head);

		/* check if all vehicles in the source train are stopped inside a depot */

		if (r < 0) return CMD_ERROR;

		num += r;

		/* check if all the vehicles in the dest train are stopped */

		if (dst_head != NULL) {

			r = CheckTrainStoppedInDepot(dst_head);

			if (r < 0) return CMD_ERROR;

			assert(dst_head->tile == src_head->tile);

		}

		/* Check that the length of the dest train is no longer than XXX vehicles */

		if (num > (_patches.mammoth_trains ? 100 : 9) && IsFrontEngine(dst_head))

			return_cmd_error(STR_8819_TRAIN_TOO_LONG);

	}

	// when moving all wagons, we can't have the same src_head and dst_head

	if (HASBIT(p2, 0) && src_head == dst_head) return 0;

	// moving a loco to a new line?, then we need to assign a unitnumber.

	if (dst == NULL && !IsFrontEngine(src) && IsTrainEngine(src)) {

		UnitID unit_num = GetFreeUnitNumber(VEH_Train);

		if (unit_num > _patches.max_trains)

			return_cmd_error(STR_00E1_TOO_MANY_VEHICLES_IN_GAME);

		if (flags & DC_EXEC)

			src->unitnumber = unit_num;

	}

	/* do it? */

	if (flags & DC_EXEC) {

		/* clear the ->first cache */

		{

			Vehicle *u;

			for (u = src_head; u != NULL; u = u->next) u->first = NULL;

			for (u = dst_head; u != NULL; u = u->next) u->first = NULL;

		}

		if (HASBIT(p2, 0)) {

			// unlink ALL wagons

			if (src != src_head) {

				Vehicle *v = src_head;

				while (GetNextVehicle(v) != src) v = GetNextVehicle(v);

				GetLastEnginePart(v)->next = NULL;

			} else {

				src_head = NULL;

			}

		} else {

			// if moving within the same chain, dont use dst_head as it may get invalidated

			if (src_head == dst_head)

				dst_head = NULL;

			// unlink single wagon from linked list

			src_head = UnlinkWagon(src, src_head);