I looked at images of the actual registers and they are duplicate entries. My guess is that the minister went from church to church and the baptism simply got duplicated on each church register by accident.
A search of the churches on GENUKI wasn't definitive. Try posting on the Middlesex mailing list (http://lists.rootsweb.ancestry.com/index/intl/ENG/Middlesex_...
) for information about these churches and why the same baptism would have appeared on three church registers.