Prior to the 1980 Limitation Act, under which one may sue for damages
for actions which have occurred within the 6 years prior to the claim,
what was the maximum time after which one could sue?  Was it more or
less than 6 years?  What was the name of the Act/Statute?

Dear martinesmith-ga,

It was six years in some circumstances, three years in others, but
could be extended subject to the court?s discretion. In fact, the law
was very confused on this issue which is why the 1980 Act is described
as ?An Act to consolidate the Limitation Acts 1939 to 1980?.
http://www.lawcom.gov.uk/docs/cp151apa.pdf

This House of Lords Appeal has a good summary of the law from 1939 to
1980 regarding commencement of civil proceedings (paragraph 5
onwards).
http://www.publications.parliament.uk/pa/ld200304/ldjudgmt/jd031204/donnel-1.htm

You will see that the first act they refer to is the Limitation Act
1939 which set the period broadly at six years. Later there was the
Law Reform (Limitation of Actions, &c.) Act 1954 which reduced it to
three years for personal injuries. The Limitation Act 1963 reduced it
to 12 months in certain circumstances. The Law Reform (Miscellaneous
Provisions) Act 1971 ?lengthened from 12 months to three years the
period within which, after the date of knowledge, a plaintiff might
seek leave to bring proceedings.? Finally, the Limitation Act 1975
gave the court discretion to extend the period if it was equitable,
for example, personal injuries actions.
The Times newspaper of the 60s and 70s carries many reports of court
cases in which the period were subject to appeal and argument. This no
doubt led to the 1980 Act to tightening up the legislation.

Incidentally, the six year limit originated in the Limitation Act of 1623.
http://www.lawlink.nsw.gov.au/lrc.nsf/pages/R50CHP2

You will find some additional background information on this
discussion of the Limitation of Actions.
http://www.lawcom.gov.uk/docs/cp151pt1.pdf

I hope this answers your question. If it does not, or the answer is
unclear, then please ask for clarification of this research before
rating the answer. I shall respond to the clarification request as
soon as I receive it.
Thank you
answerfinder