Mystery frame ID help

[Johnny Ragwort]

I've just bought this beastie off Ebay (mostly because I wanted the forks for another project) and I'm wondering what it is. It seems to be 531 - seat tube internal diameter is 27.2 and there's a 531 sticker on the forks (not that that means much as it's been refinished at least twice) - but beyond that I'm a bit stumped! The wraparound seat stay may be an indication to those who know more than I do.
I think it might be a half way decent frame. Frame and forks together weigh around 2.7kg and the dropouts are Campagnolo. It came with a Campagnolo headset too, which is in reasonable order. It was valued enough by someone to have it refinished by a company called Autostrada Engineering, who were based in Birmingham: the old invoice was rolled up in the seat tube. I was hoping the make would be somewhere on it, but all I can make out is that it was resprayed in flam red with a white panel on the seat tube. The number stamped on the bottom bracket shell is also stamped on the steerer tube. I'd love to know what it might be, if anyone has any ideas!

 

[hamster]

Looks lovely - nicely filed lugs and wrapover stays. First thought would be Carlton, but I'm no expert on the marque.

 

[Midlife]

Shorelines of the lugs and wrap round brazing look fab, doesn't pin it down to any individual but knew what they were doing any pics of the dropouts

 

[vcballbat]

Photo of the fork and crown, front and rear dropouts and cable guide on rear chainstay would be a great help. Shares some features of my 1961 Jensen Italia though my frame number starts with 61 which denotes the year...nice frame. ☺

 

[vcballbat]

Lugs, wrap around seat stays and over bottom bracket cable guide look similar...

https://www.retrobike.co.uk/threads/jensen-italia-1961.337691/

 

[Johnny Ragwort]

Fork crown and dropout pics, as requested. That Jensen does look similar in some respects! I've also noticed that in addition to the serial number on the bottom bracket shell and steerer tube, there's also the number 3 stamped into both.
Whatever it is, I'm beginning to think it's too good to rob the forks off, and is certainly better than the Fred Williams frame I was going to use them on.

 

[torqueless]

Could be a Mercian? A 1973 one. I think you can still ask them?

 

[Johnny Ragwort]

Could be a Mercian? A 1973 one. I think you can still ask them?

I'd be very chuffed indeed if it was a Mercian, as I only paid fifty quid for it! I've just found this quote on Classic Rendezvous... "Mercian frame numbering consists of the number of the frame built that year followed by the year of manufacture, sometimes this system was reversed to have the year of manufacture first... also there should be a single number near the main frame number denoting the builder of the frame.", which fits what I've got: my frame and forks both have the frame number with the number "3" stamped nearby but obviously separate.

 

[biggs682]

Last time i asked Mercian about a 70's frame they replied saying lost in a fire but well worth asking

 

[Nob]

I was going to say Major Nichols Frame but then it could well be a Mercian…