What was the conclusion of the Board of Trade inquiry?

The Board of Trade issued two reports at the end of the inquiry: one authored by the chair, Mr Rothery and the other by the two assessors, Colonel Yolland and Mr Barlow.

They agreed about most of the issues in contention:

1. There is no evidence to show that there has been any movement or settlement in the foundations of the piers;
2. The wrought iron was of fair quality;
3. The cast iron was also fairly good, though sluggish on melting;
4. The girders were fairly proportioned for the work they had to do;
5. The iron columns, though sufficient to support the vertical weight of the girders and trains, were owing to the weakness of the cross-bracing and its fastenings, unfit to resist the lateral pressure of the wind;
6. The imperfections in the work turned out at the Wormit foundry were due in great part to want of proper supervision;
7. The supervision of the bridge after its completion was unsatisfactory;
8. If by loosening of the tie bars the columns got out of shape, the mere introduction of packing pieces between the gibs and the cotters would not bring them back to their positions;
9. Trains were frequently run through the high girder at much higher speeds than at the rate of 25 mph;
10. The fall of the bridge was probably due to the giving way of the cross-bracing and its fastenings.
11. The imperfections in the columns might also have contributed to the same result.

(Rothery report)

Rothery went on to look at specific design problems in the bridge, especially the narrow base, the slight inclination of the outer columns and to the omission of spigots at their bases, and to the casting of holes in the lugs and flanges of the 18 inch columns. He laid the blame for faulty design, construction and maintenance at Bouch’s door. The other two members of the inquiry did not go so far, but felt strongly enough to produce a second joint report on the disaster.