A few other interesting multiple unit formations that i have stumbled across online recently.
Class 314 + Class 318 formation can be seen in this video here:
I have heard that a 314 + 320 has also happened but i can not find any videos or photos.
Class 314 + Class 322 formation can be seen in this video here:
I believe these were fairly common on ECS moves but i do not think it ever happened in passenger service.
There was also a rare occassion of a 317 + 322 formation on the GEML here:

I presume that a 317 + 321 formation has likely happened at some point too.
There was also this weird temporary one carriage 142 plus one carriage 143 or 144 formation at one point:

This may well be the only occassion that two different pacer classes formed a hybrid.
It seems that a rare 12car class 156 formation has happened at least once in the past:

I thought the 10car 158 and 159 that SWR run was a record for the longest sprinter but it seems not.
It seems like the odd mismatched Sprinter formations were more common than i thought:
There was also some 3car 156 sets similar to the current 3car 150 sets that Northern have or the 3car 158 sets that GWR have. Plus some temporary 150+153 and 150+156 and 150+158 formations have happened on dozens of occassions. This article gives a good overview of many of the occassions.
Some more photos of the various unusual formations that i have found online:









I wonder whether the class 151 was ever involved in any hybrid formations. Or did it at least couple to any other sprinter or pacer units. I can only find photos of the class 151 units working on their own but none coupled to other classes.
Class 314 + Class 318 formation can be seen in this video here:
I have heard that a 314 + 320 has also happened but i can not find any videos or photos.
Class 314 + Class 322 formation can be seen in this video here:
I believe these were fairly common on ECS moves but i do not think it ever happened in passenger service.
There was also a rare occassion of a 317 + 322 formation on the GEML here:

I presume that a 317 + 321 formation has likely happened at some point too.
There was also this weird temporary one carriage 142 plus one carriage 143 or 144 formation at one point:

This may well be the only occassion that two different pacer classes formed a hybrid.
It seems that a rare 12car class 156 formation has happened at least once in the past:

I thought the 10car 158 and 159 that SWR run was a record for the longest sprinter but it seems not.
It seems like the odd mismatched Sprinter formations were more common than i thought:
There was also some 3car 156 sets similar to the current 3car 150 sets that Northern have or the 3car 158 sets that GWR have. Plus some temporary 150+153 and 150+156 and 150+158 formations have happened on dozens of occassions. This article gives a good overview of many of the occassions.
Some more photos of the various unusual formations that i have found online:









I wonder whether the class 151 was ever involved in any hybrid formations. Or did it at least couple to any other sprinter or pacer units. I can only find photos of the class 151 units working on their own but none coupled to other classes.
