def find_deepest_string_in_list(nested_list: list) -> str:
    # breadth first search
    while True:
        curr = []
        strings = []
        for x in nested_list:
            if isinstance(x, str):
                strings.append(x)
            elif isinstance(x, list):
                curr.extend(x)
        if not curr:
            return strings[0] if strings else None
        nested_list = curr