Key Points:

Helen Clark became the longest serving Labour leader in New Zealand history last Friday - or did she?

The case rests on when Harry Holland was elected leader. Mr Holland was the previous longest serving at 14 years and two months. It is accepted that he was elected Labour leader in August 1919 and died while he was still leader, on October 8, 1933.

That is a little unusual given that his predecessor, Alfred Hindmarsh, died eight months earlier, on November 13, 1918. Historians and Labour Party records can find no reference to Mr Holland having been leader earlier than August 1919.

There is evidence that he was elected "chairman" of the parliamentary Labour Party in August 1919 and was referred to as the leader after that.

If that is the time at which it is considered he became leader, then Helen Clark has surpassed his record.

And at the most conservative estimate of August 1, 1919, Mr Holland was leader for 14 years and 68 days.

Helen Clark took over the leadership on December 1, 1993. On February 8, last Friday, she had been leader for 14 years and 69 days.