Gaps reporting

        SELECT [RespondentId], [StartDateTime], [EndDateTime]
    INTO [tmp].[RESULT]
    FROM (
        SELECT [RespondentId], [StartDateTime], [EndDateTime]
            FROM
            (
                SELECT  [RespondentId],
                        [EndDateTime] AS [StartDateTime],
                        LEAD(StartDateTime) OVER (PARTITION BY [RespondentId] ORDER BY [StartDateTime]) AS [EndDateTime]
                FROM @INPUT
            ) A
        WHERE [A].[EndDateTime] IS NOT NULL
          ) AS B
    WHERE ABS(DATEDIFF(mi, [EndDateTime], [StartDateTime])) <= @GapSize