The Chronology of PT/35(b): 11 April 1990

11 April 1990

No samples removed, but DP/11 re-potted.

By previous appointment, Williamson and Harrower met Allan Worroll (S5586),
chief chemist at Ferranti Computer Systems, Oldham, who examined DP/11
microscopically and suggested further tests that could be done at Manchester
University, and it was agreed that the officers would return at a later date to have
these test carried out (in Williamson’s ch 10 CP dated 1711 1/99 he said that Worroll
was unable to arrange an appointment with Manchester Uni immediately, hence the
agreement that the tests be carried out at a later date). Worroll’s HOLMES statement
goes into more detail about what he saw, stating that he saw PT/35(b) and the curved
edge appeared to be professionally milled; and there were two edges which were
broken off and charred as if exposed to heat (in his ch10 CP Worroll stated that he
was in no doubt the fragment was heat damaged and he had seen such an effect before
in his career, as accidents did happen); solder mask had been applied to both sides of
the board. He also examined DP/11 and noted that its position in the potting made it
difficult to examine, so he re-potted it and reground it to facilitate better optical

DP-35 Page 2

DP-35 Page 2

He confirmed that the board was made of fibreglass laminate constructed
with nine layers of glass cloth and the board appeared to be single-sided (i.e. copper
tracks on only one side) as there was no evidence of “through hole plating” (in his
ch10 CP Worroll stated that his view that it was single-sided because there was no
evidence of through hole plating was “simply instinct”, as there was no circuitry on
the reverse of the fragment). He suggested that there was solder mask on both sides
of the board and stated that this was a mystery as he could see no reason for the
application of solder mask to both sides of a single sided printed circuit board. The
suggestion that the board had solder mask on both sides is contradicted by other
witnesses (see 9 March above and 14 June below; the RARDE report also suggests
that the board had solder mask on one side only; in his ch10 CP Worroll himself said
it was only solder masked on one side – see in this section below). Worroll then
refers to being told by police that previous examination had revealed that the copper
tracks were lined with tin only as opposed to a tin/lead combination which would be
more normal, and that previous examinations had most closely matched the fragment
to two samples, and Worroll suggested that he make arrangements with the Dept of
Science and Technology at the University of Manchester, which could use Secondary Ion Mass Spectrometry test equipment to very accurately tell if the fragment matched
the two samples. According to Harrower’s ch10 CP, as a result of the discussion with
Worroll and a suggestion made by him that they pursue the construction of the
conducting tracks, as they appeared to be pure tin rather than a mixture of tin and
lead, the police went to Siemens, Munich (see below).

Williamson’s memo to the SIO dated 16 March 1990, which was clearly updated after
that date, also mentions that Worroll had identified some evidence, a long scratch-like
mark, across the large pad on the fragment, which suggested that a thin insulated wire
could have been soldered to the pad, there being the part profile of a wire having been
laid across the pad when partial fusion of the tin occurred leaving the impression of a
thin wire lead. This might be consistent with what Williamson’s memo records Dr
Wilkinson as having seen – the cylinder which she thought could have been the
remnant of where a wire had been embedded in the solder. (see under 2 March 1990, above)

In his defence precognition Worroll states that the police were interested in knowing
if the fragment came from a board made on a production type process or if it could
have been the work of an individual working alone using more basic procedures, and
Worroll’s view was that the general finish and machining of the fragment, the
appearance of the metallic circuitry and the constituent substances used, including the
fact that the solderable finish was tin and lead as opposed to just tin, made Worroll
think it was from a production line process. His ch10 CP refers to this question of
whether the fragment was manufactured commercially or not, and he says that he had
looked at a cross-section of the tracking to see the track profile, as commercially
produced tracks tend to be clean and almost vertical, whereas domestic manufacture
tends to have a sloping profile. He suggests that the examination he carried out was
inconclusive, the track profile was fairly good, suggesting commercial manufacture,
but he could not discount that it was done domestically by an expert. He later refers
to the curved edge having been machined rather than hand cut. The PF in a note
stated that this contradicted Worroll’s original statement (in that he originally said the
track profile suggested it was a homemade board, although the milled curve was
indicative of professional manufacture). Worroll examined PT/35(b) and confirmed
he had signed the label. He stated that from this examination he could confm that
the solder mask appeared only on the reverse side, and said this was apparent due to
the green appearance of that side. He said it was unusual for a board to have solder
mask on the reverse side as it is normally used for protecting tracking and circuitry.
He could not think of any reason for it to be applied on the reverse side. He examined
DP/11 and said it bore the hallmarks of his work although he could not recall why the
fragment had been cross-sectioned at the particular angles they had been. Worroll
gave evidence but it added little to what is noted here, and the terms of his evidence
were rather vague: Worroll seemed still unable to recollect that he had removed the
solder mask from DP/31 (see 23 May 90, below) and appeared to get confused about
what he was being asked. He did state in evidence that solder mask was only visible
on one side of the fragment.

Worroll’s statement and the police report have this first visit to Ferranti dated 11 May
90, but Williamson and Harrower’s statements date it at 11 April 90. Worroll’s
statement refers to the police attending on a second occasion on 23 May 90 (below)
and being advised that since the last visit, DP/31 had been removed from the fragment
by Siemens. As the removal of DP/3 1 occurred on 27 April 90, it would suggest that
the first visit to Ferranti was before that date, which would indicate that 11 April was
the correct date for this first visit. Also, Worroll’s statement concurs with those of the
officers by referring to the day of the first visit as a Wednesday. In fact 11 April was
a Wednesday but 11 May was a Friday, again indicating that the earlier date is the
correct one.

As stated above, according to the CP and DP of Paul Boyle of New England
Laminates (see under 14 February above) he was visited again by police who had with
them DP/11, which by this stage had been altered. It seems apparent that, assuming
Paul Boyle is correct in his memory (which it seems he must be, given that DP/11 was
indeed altered by Worroll) then this return visit to see Boyle must have been after
Worroll had altered the position of DP/11. As stated above, there is no record of this
return visit to New England Laminates.

NB Worroll was also seen by police in 1992 and asked to examine a control sample
MST-13 circuit board – see 5 March 1992 below. NB Worroll’s signature is visible
on the label for DP/11 and for PT/35(b).

This entry was posted in Chronology, PT/35(b). Bookmark the permalink.

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