In the UK, the 1950 Allotments Act trumps all other covenants and local ordinances, provided you're only keeping hens and they are not a nuisance (and despite the name, the Act in this instance applies to keeping hens anywhere).
Could you just confirm that for me - a deed of covenant is unable to restrict the keeping of hens in UK law?
I ask because I'm pretty sure out deed of covenant says 'no chickens'. It might also be 'no sheep'. Don't suppose the Allotments Act covers sheep though.
Well you can read the Act, it's quite short and written in reasonably plain English.
The relevant section is S12.1 (S12.2 has been repealed). It only applies to hens (female chickens) and rabbits, not to any other species. It appears to supersede any covenants. As far as I know this aspect of the Act has never been tested in court.
http://www.legislation.gov.uk/ukpga/Geo6/14/31