def Crossing1Files(fileName, ind=None):
    """
    Takes a filename of the structure used for the Crossing 1 videos - YYYMMDD_hhmmss-suffix.mkv
    Retrieves the datetime of the start of the video

    Input:
        fileName: Name of the file
        ind: Indicator of whether it is the left or right crop of the video which is wanted. Optional

    Output:
        datetime: String of the format  DD-MM-YYYY hh:mm:ss
    """

    date = fileName[:8]
    time = fileName[9:15]
    
    if ind:
        if ind == "left":
            if "right" in fileName:
                return None
        elif ind == "right":
            if "left" in fileName:
                return None
    
    datetime = "{}-{}-{} {}:{}:{}".format(date[6:8], date[4:6], date[:4], time[:2], time[2:4], time[4:6])
    
    return datetime