I suspect she is arriving back at Belfast after her sea trials. Note the deployed safety boat No.1. Here are coloured versions of the same pic. Note the so called "smudge"?
The only way there would have been a "smudge in that area would have been as I have suggested: due to contact with a tug's bow fender or by contact with some other type of immoveable object. In that area, most certainly would not have been caused by fire of any kind.
Now look at the same picture with the WT bulkhead "F" between BRs 5 & 6 added: