For better or worse. here's the complete report on the Dover Ferry incident.
Note that this is not the court findings, nor do they feel bound be court
precedents, or make any attempt to place blame. The actual prosecution was
much more limited in scope, and only found fault under Rules 5 and 19.

It would be possible to find something in this report to support almost any
position.

On the issue of safe speed:

"Recognising that there is always a possibility that small vessels and other
floating objects might not be detected by radar at an adequate range (Rule
6(b)(iv)), it follows that a speed which relies on radar for detecting vessels
at a
sufficient range so as to be able to avoid collision, in accordance with the
Collision Regulations, should not be regarded as a safe speed.

"However, the practicality of following the above criterion in conditions of
severely restricted visibility is questionable (eg the need to maintain steerage
in
conditions of zero visibility). Additionally, the commercial viability of
shipping
would be in danger of being undermined if the criterion was strictly applied,
particularly in areas prone to restricted visibility.

"In view of the above, a more pragmatic approach might be appropriate, such
that a degree of reliance on radar for detection might be acceptable following a
reasoned assessment of the risks in doing so."

http://www.dft.gov.uk/stellent/group...ety_507877.pdf