The Maltese Cross cancellations served for almost four years before they were superseded, in 1844, with “barred numeral” cancellations, so called, as they compromised a series of horizonatal lines with a number in the centre to signify the Post Town that had cancelled the stamp(s).

This idea is accredited to Francis Abbot, a Senior Clerk at the General Post Office, who had earlier suggested that each significant Post Town be allocated an individual numer.  Due to the high number of Post Towns requiring a unique number, five different designs were adopted.
 

London Inland Office

The Inland Office dealt with items posted in London and addressed to locations outside London.

The format of the cancellation for the London Inland Office was that of an oval with the number in the centre inside a diamond.  Initially, numbers 1 to 20 were allocated and these cancellations came into use on 17 May 1844.
 

London District Office

The District Office dealt with items posted and to be delivered to addresses within London.

The format of the cancellation for the London District Office was that of an oval with the number in the centre inside a circle.  Initially, numbers 1 to 72 were allocated with 50 to 72 being used at the chief office; the lower numbers were used at Suburban Offices and Receiving Houses.  These cancellations came into use on 21 May 1844.
 

English and Welsh (provincial) Post Towns

The format of the cancellations for English and Welsh towns (excluding London) was that of an oval with the number in the centre.  Initially, numbers 1 to 942 were allocated and sent to Post Towns in April 1844.  These cancellations came into use on 1 May 1844.
 

Scottish Post Towns

The format of the cancellations for Scottish Post Towns was that of a rectangle with the number in the centre. Initially, numbers 1 to 342 were allocated.  These cancellations came into use on various dates as they were received; the earliest recorded being dated 19 June 1844 used in Glasgow.
 

Irish Post Towns

The format of the cancellation for Irish Post Towns was that of a diamond with the number in the centre.  Initially, numbers 1 to 450 were allocated.  These cancellations came into use on various dates as they were received; the earliest recorded being dated 20 June 1844 used in Dublin.
 

Usage on the 1840 1d Black
 

Although the 1d black had been replaced in February 1841 by the 1d red-brown, it remained valid for postage and is occasionally seen with a barred numeral; such usage, however, is rare.