Amalgamated Investment v Texas Commerce International Bank [1981]

AIP requested bank forward money to their subsidiary.
To avoid restrictions, bank forwarded money via their
own subsidiary.
AIP had given guarantee to repay bank any money bank forwarded to AIP’s subsidiary.
As this turned out to be none, AIP did not pay.
Court of Appeal held guarantee, on its true construction,
applied to loans via bank’s subsidiary.
But even if it did not, plaintiff estopped from
denying the fact by an estoppel by convention:
Both had assumed guarantee would cover loans via
bank’s subsidiary.
Two main points:
1.  Although estoppel
by convention differs from promissory estoppel in that no representation
needed, judgments indicate that different forms of estoppel could be merged
together into one general principle shorn of technicalities.
2.  Even though
strictly it was AIP who brought the claim (for declaratory relief), bank was
effectively founding cause of action on estoppel.

But Brandon LJ stated that whilst plaintiff
could not found an action on an estoppel,
he may, as result of being able to rely on estoppel, succeed on a cause of action
which otherwise would have failed.