A major problem on the Post Office's Horizon IT system - built by Fujitsu - floored transactions for two 30 minute periods yesterday, as tens of thousands of customers queued in branches to send their Christmas parcels.
The Horizon point of sale system has been the source of much controversy over allegedly problematic accounting - resulting in an angry legal battle with sub-postmasters who say they have been wrongly accused of fraud - andin criticism by parliamentary committees that have questioned its cost.
The Post Office insisted the Horizon service was fully running today. No explanation has been given by the Post Office as to the exact nature of the problem, or how it was fixed. But given the weight of usage yesterday, major concerns are being raised around the system's capacity.
The Post Office said only that it was "very sorry", and Fujitsu declined to provide any comment.
The Horizon system has experienced other serious difficulties this year, with a shutdown in July locking out over 3.3 million Post Office card customers, including pensioners looking to access their latest instalment.
It is also the subject of a legal battle, after local sub-postmasters - who have been accused of fraudulent accounting - blamed the system for the errors they are accused of making. The Post Office has denied the accusations.
In separate IT issues, last week Royal Mail double-charged some website customers, and its Price Finder stamp selling website has experienced major errors and outages for three weeks - following a botched server migration.