THE case of the Calderstones Hospital patient jailed for a sex attack on a woman nurse being classed as 'too dangerous' to be there in the first place raises disturbing concerns.

In itself, the incident demands investigation. There needs to be an explanation why this man was sent to Calderstones' medium-secure unit after a similar offence in December and whether this was appropriate when, before he attacked the nurse, he himself had warned that his uncontrollable sexual urges could make him re-offend.

But if this patient, now imprisoned pending transfer to a maximum security mental hospital, ought never to have been at the Whalley hospital to begin with. The crucial question that arises is: how many other patients are there at Calderstones who may present similar danger to others?

Ribble Valley MP Nigel Evans is right to demand a full safety review in order to provide the answer and to ensure that such a disturbing incident many not happen again.

It is not just that, as Community Health Council chief Nigel Robinson warns today, that improper care affects both patients and staff, but also that the community must be satisfied that patients at Calderstones pose no danger to them -- above all, when new housing is being created cheek by jowl with its medium-secure unit.

It may be true that many of the hospital's patients have never been ordered there by the courts. But since it is also the case that convicted sex offenders, killers and arsonists are in the category accommodated at its medium-secure unit, there needs to be absolute reassurance that it is the appropriate place for them -- and the public.

Lapses in the unit's security revealed by previous incidents this year -- including the absconding of a patient believed to be a convicted arsonist who was later found with a lighter; another found in a pub 35 miles away after going on the run; and the case of another wounding a fellow patient -- all beg a review of the security at the unit. And this latest disturbing incident adds to that demand -- above all, to determine who should or should not be there in the first place.