I am writing an academic textbook and want to incorporate a cartoon first published in Punch in 1908, called 'The Caravan Craze' The artist, George Morrow, died in 1955, so I presume copyright still exists under the 70 year rule..
Although I have found copies of the cartoon for sale as framed pictures, I can't trace who holds copyright in the original. It isn't on the Punch website, nor can I find it in the British Library collection.
Yes I think it would be wise to assume that the cartoon is still in copyright. As for tracing the current owner of the rights, as you have searched the British Library archive and www.punch.co.uk without success, the only other place I can suggest is the Gale archive. The way the original Punch content was divided up between the various parties is somewhat confusing, and so I don't know whether there are any other repositories which you could search. If the Gale archive gets you no further, I would suggest contacting the British Library and trying to speak to/correspond with the curator of their Punch collection as that person will no doubt have some knowledge about the other parts of the total archive.
If all that fails to produce a source from whom you can obtain a licence, you may need to conduct a diligent search to try to find the heirs of George Morrow. There is an entry on the Probate search website for a George Morrow of Thaxted, Essex who died on 18 Jan 1955 but I have no idea if this is the artist of the cartoon. If it was, probate was granted to Arthur Graham Blunt, solicitor, and Mabel Smith spinister. Ultimately if you cannot trace any copyright owner following a reasonably diligent search, you could apply for an orphan works licence from the Intellectual Property Office which would allow you to re-publish the cartoon without incurring liability for infringement.
I'm in a similar position, intending to use in an academic book a cartoon from Punch from 1901 by the artist Leonard Raven-Hill (1867-1942). Now, since the artist has been dead for more than 70 years, could I reproduce the cartoon on the basis that copyright has expired?
Yes, you can copy and re-use the original cartoon. However, take care over where you source the cartoon, or more accurately, a digital version of it. This is because some bodies which have scanned and digitized the cartoons often claim to hold copyright in the digital copy, because, they say, they have created a new work. Such claims usually fail to stand up because the scanning process employed lacks the necessary human creativity which is a key ingredient for copyright*. However since these bodies make money from licensing their digital images, they will often threaten to sue for copyright infringement, even though they know they are on shaky ground legally speaking, in order to protect their business model.
Therefore if you can find an original printed version of the cartoon and make your own digital copy you should avoid the hassle of becoming embroiled in legal threats. I imagine that there a a good number of libraries and archives which still retain original Punch magazines from which a scan or digital photograph can be made.
* See page 3 of this Copyright Notice from the Government's Intellectual Property Office for more details about scanned images of older, out-of-copyright images.