Royal Mail tracking number format

13 alphanumeric string starts with 2 characters followed by 9 digits and ends with 2 characters. The last 2 characters are "GB"    

Parcel Force tracking number format

13 alphanumeric string starts with 2 characters followed by 9 digits and ends with 2 characters.    

Valid prefix: EA,EB,EC,ED,EE and CP    

Royal Mail tracking number example

RJ733259145GB
RJ733258817GB
JV654386368GB
RS907419159CH
RZ435403332GB
RZ421569371GB

Parcel Force tracking number example

EE698742743GB
EE584464110GB
EK333490866GB
EK408553403GB
EK333487972GB
CU140746133GB
LA540591358GB
EH635000002GB
EK333672121GB
EK880068995GB