What are these?

At first look I thought they were Tridents because of the slightly flattened cross-section in front of the cockpit. But the cockpit window frames are certainly not Trident – unless, of course, there’s some sort of temporary jig in place. Can anyone confirm?
The picture’s from the front cover of a new book I was given today, Memories of the Lancashire Aircraft Industry (Countryside Books, £12.99). There are some good personal recollections, but the description on the back “well-researched” is misleading.
The front cover picture (see above) has no caption or explanation – were Trident forward fuselages made in Manchester? – and if you’re the kind of person like me who gets all hot and bothered at seeing a dH5 captioned as an Avro 504K, or Samuel Pierpoint Langley’s Aerodrome dropped in for no reason whatsoever, then give it a miss.