def find_longitude_wrap_start(packed_data_item):
    """
    ONLY WORK OUT THE WRAP START OF THE DATA
    :param packed_data_item:
    :return:
    """
    from iris.exceptions import CoordinateNotFoundError
    try:
        x_points_min = packed_data_item.coord(standard_name='longitude'
            ).points.min()
    except CoordinateNotFoundError:
        x_wrap_start = None
    else:
        x_wrap_start = -180 if x_points_min < 0 else 0
    return x_wrap_start
