This guidance assumes that the verbal tenancy was created after 28 February 1997 (and is therefore an assured shorthold tenancy). If the verbal tenancy was created before this date, contact the Guild.
Because the tenancy is a verbal tenancy, there is a little housekeeping needed doing before serving notice and issuing proceedings.
Step 1 – Section 48 Notice
The landlord must serve on the tenant a section 48 notice. The effect of failure to serve a notice is that the landlord is not entitled to recover the rent contractually due, nor to succeed in proceedings that require him to establish arrears of rent or failure to pay rent. [Drew-Morgan v Hamid-Zadeh  L. & T.R. 503.] An oral notice is insufficient. [Rogan v Woodfield Building Services (1995) 27 H.L.R. 78.]
s 48 Notification by landlord of address for service of notice
(1) A landlord of premises to which this Part applies shall by notice furnish the tenant with an address in England and Wales at which notices (including notices in proceedings) may be served on him by the tenant.
(2) Where a landlord of any such premises fails to comply with subsection (1), any rent, service charge or administration charge otherwise due from the tenant to the landlord shall (subject to subsection (3)) be treated for all purposes as not being due from the tenant to the landlord at any time before the landlord does comply with that subsection.
The notice should be posted and get a free of charge certificate of postage from the post office.