en in particular cases, as for
instance for an overdraft on one account against another which had
habitually been kept and operated on separately. It equally prevents the
dishonouring of cheques in circumstances in which they have hitherto been
paid independent of the actual available balance.

Restrictions arising from course of business can of course be put an end to
by the banker, but only on reasonable notice to the customer and by
providing for outstanding liabilities undertaken by the latter in reliance
on the continuance of the pre-existing state of affairs (see _Buckingham_
v. _London & Midland Bank_, 12 Times L.R. 70). As against this, the banker
can, in some cases, fortify his position by appeal to the custom of
bankers. The validity of such custom, provided it be general and
reasonable, has frequently been recognized by the courts. Any person
entering on business relations with a banker must be taken to contemplate
the existence of such custom and implicitly agree that business shall be
conducted in accordance therewith. Practical difficulty has been suggested
with regard to proof of any such custom not already recognized in law, as
to how far it can be established by the evidence of one party, the bankers,
unsupported by that of members of the outside public, in most cases
impossible to obtain. It is conceived, however, that on the analogy of
local custom and the Stock Exchange rules, such outside evidence could be
dispensed with, and this is the line apparently indicated with relation to
the pass-book by the court of appeal in Vagliano's case (23 Q.B.D. at p.
245). The unquestionable right of the banker to summarily debit his
customer's account with a returned cheque, even when unindorsed by the
customer and taken by the banker in circumstances constituting him a
transferee of the instrument, is probably referable to a custom of this
nature. So is the common practice of bankers to refuse payment of a
so-called "stale" cheque, that is, one presented an unreasonable time after
its ostensible date; although the fact that some banks treat a cheque as
stale after six months, others not till after twelve, might be held to
militate against the validity of such custom, and lapse of time is not
included by the Bills of Exchange Act among the matters working revocation
of the banker's duty, and authority to pay his customer's cheque.
Indirectly, this particular custom obtains some support from sec. 74 (2) of
the Bills