Yes, attempted suicide (and perhaps suicide) was a crime. Several formal and informal sources confirm the sentence of imprisonment for attempted suicide.
See section 1.3.1 and 1.3.2 of this PDF. It confirms the existence of a law(but not the quantum of punishment) and its overruling in 1961.
I found a paper "Suicide as a crime in the UK: legal history, international comparisons and present implications" by J. Neeleman. The paper specifically states the following:
However, R. v. Mann (1914) finally clarified that suicide was a
felony and that attempted suicide was a misdemeanour, punishable by
imprisonment and hard labour. Penal sanctions against suicide
attempters continued to be implemented until as recently as 1955 (6),
From this article, which references the above paper:
Historically, suicide was deemed
self-murder and those who attempted
suicide were subjected to punishment.
However, it became recognised that the
mental state of suicide attempters
needed to be taken into account and
that imprisonment should only be
considered in the interests of their
health and well being (R v Doody
1854). Imprisonment as a punishment
for attempted suicides was being used
up until the late 1950s. Some concern
had been expressed by magistrates over
the use of such punishments (R v
Trench 1955) and changing social
attitudes brought a more compassionate
attitude to those who attempted
suicide (BMA 1959). Prosecuting those
who failed in a suicide attempt did
not assist them in their recovery.
There was a call by the British
Medical Association and the
Magistrates’ Association to amend the
law, in line with the situation in
Scotland, so that attempted suicide
should cease to be an offence (BMA
1959). Subsequently, suicide was
decriminalised by the enactment of the
Suicide Act 1961.
Some informal sources also confirm imprisonment as the sentence for attempted suicide.
From wikipedia (unreferenced):
Suicide may be defined as the act of
intentionally ending one's own life.
Prior to the Suicide Act 1961 it was a
crime to commit suicide and anyone who
attempted and failed could be
prosecuted and imprisoned, while the
families of those who succeeded also
could potentially be prosecuted
From answers.com (again unreferenced):
Suicide is not against the law in the
UK. It was until the 1961 Suicide Act
which legalised it and introduced laws
which dealt with assistance of
suicide. Prior to 1961 suicide was
illegal in the UK and was punishable
by prison and fines (but not death!)