The 1990 published edition of "Lloyds War Losses – The First World War", has a forward written by the Librarian at the Guildhall Library (London), who notes the discrepancies in the numbers of vessels lost in different publications. She claims that the official Merchant Shipping Losses (often referred to as "British Vessels Lost at Sea") is “…neither comprehensive or detailed” with errors and omissions.
She believed that it is likely that some of the differences came from the fact that the fate of some ships was not clear – for example several vessels are listed by Lloyds as Missing or Untraced and are not counted as War Losses, although some were later confirmed as a loss through enemy action.
She continues that it is also the case that some vessels, in the Admiralty lists as total losses, are recorded elsewhere as damaged, having been salved and towed into harbour, although some were later written off as losses.
There was also the question of ships detained or captured by the enemy: as some of these were later recovered, were they counted as losses?