Table Of ContentTHE LAW OF WAIVER, VARIATION, AND
ESTOPPEL
THE LAW OF WAIVER, VARIATION, AND
ESTOPPEL
SEAN WILKEN QC
BA (Oxon); Dip Law; Barrister of the Middle Temple
KARIM GHALY
BA (Oxon); Barrister of the Inner Temple
Great Clarendon Street, Oxford ox2 6DP
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FOREWORD TO THE FIRST EDITION
One of the greatest strengths of the common law lies in its versatility, its responsiveness to new
problems. This permits a freshness of approach, an ability to tackle a novelty without the need to
force it into a codified doctrinal mould. When the responses to individual needs have been numerous
enough it may be possible to detect a pattern, from which there can be deduced a general principle
capable of direct application in subsequent cases.
This oft-celebrated virtue of the common law is, however, fallible in two respects. First, where an
attempt to generalise imposes on the instances a unity which does not exist, representing them as
examples of an underlying principle which they do not truly represent. Second, at the other extreme,
where a common thread which really does link the individual examples goes unrecognised, perhaps
because the instances are too widely scattered to fit into any but the widest perspective, or perhaps
because the adversarial system of law-making cannot succeed unless all the necessary materials are
before the court.
These strengths and weaknesses are a particular feature of the area (or, it may be, the areas) of law
discussed in the present work. Somewhere behind all the doctrines variously identified as estoppel,
waiver, and so on lies a human instinct, implicit in all developed legal systems, which finds it
distasteful that the law should enable someone to have it both ways, to blow hot and cold, to change a
settled course of conduct, or an expressed intention, to the unfair detriment of another. This concept is
universal, but it cannot be given full rein without creating more problems than it solves. The question
is to map the boundaries, and the instances have been so widely dispersed, the examples from one
field so inadequately deployed in another, the language of the judgments so various, that the
translation of the instinct into accurate rules of law has yet to be achieved.
This is why the topics discussed in this book are so hard to manage. All those who have handled them
in practice will know that doctrines such as estoppel can be powerful and yet dangerous weapons. The
challenge is to set the boundaries for their proper use, and this task requires a disciplined study of
materials drawn from a wide range of sources.
The fruits of just such a study are evident in this book. It does not attempt the impossible in the shape
of a fully worked-out theory, capable of reconciling all the reported cases. What it does achieve is a
methodical survey of the law—and particularly of commercial law, where the doctrines are of special
practical importance—from which practitioners of all kinds in many different fields may find
instance and commentary ready at hand for the tasks before them.
The book will be a boon, and I am glad to commend it.
M. I. MUSTILL
PREFACE
This is the Third Edition of this book. In writing it I have had the considerable and essential
assistance of Karim Ghaly who is primarily responsible for Chapters 9, 11, 12, 14, 17, 19, and 22 and
sets out his own thanks below.
The transition to the Third Edition was always going to be a difficult task—much of that difficulty
being self-inflicted as a result of the almost exactly 10-year gap between the Second Edition and this.
The result has been a complete rethink and substantial rewrite of much of the book.
I am therefore very grateful to my Chambers in allowing me the time to carry out that task and to the
staff at Oxford University Press for their assistance.
In carrying out the research, I have also had the invaluable assistance of Rebecca Drake and Rachael
O’Hagan from my Chambers.
As usual, however, all errors are my own.
As before, the line is drawn in the shifting legal sands as at 28 July 2011.
SW
16 August 2011
London
As a new addition to the spine of this book, I owe a substantial debt to Sean for the text I have
inherited and for his help in making sense of the developments in this field over the past decade.
I am grateful to Oxford University Press for their assistance during the writing process and to
Chambers for allowing me the time to work on my sections of this edition (in particular, our clerks,
David Barnes and Owen Lawrence, for not holding me to my original time estimate).
In carrying out the research, I too have had the invaluable assistance of my colleagues, Rachael
O’Hagan and Rebecca Drake. All errors are, however, my own.
KG
28 July 2011
London
CONTENTS—SUMMARY
Tables of Cases
Tables of Legislation
1. Introduction
2. Variation
3. Waiver (I)—Terminology
4. Waiver (II)—Types of Waiver and Their Elements
5. Waiver (III)—Complexities
6. Election, Affirmation, and Acquiescence
7. Estoppels—A General Introduction
8. Equitable Forbearance
9. Estoppel by Representation
10. Estoppel by Convention
11. Proprietary Estoppel
12. Estoppel by Deed
13. The Anomalies—The Panchaud Frères ‘Doctrine’ and Contractual ‘Estoppel’
14. Procedural Doctrines—Res Judicata, Issue Estoppel, and Abuse of Process
15. Commercial Law
16. Agency
17. Banking Law
18. Company Law
19. Construction Law
20. Insurance Law
21. International Trade, Sale of Goods, and Shipping
22. Landlord and Tenant
Bibliography
Index
CONTENTS
Tables of Cases
Tables of Legislation
1. Introduction
A. Complete Doctrines?
(1) Links to other doctrines?
(2) A unified theory?
(3) A series of interlocking doctrines?
B. The Scheme of the Text
2. Variation
A. Introduction
B. Terminological versus Actual Distinctions
C. Requirements for a Variation
(1) A valid and subsisting contract
(2) Consensus as to the obligations which are altered
(3) Action to benefit or detriment
D. Difficulties Associated with the Doctrine
(1) The effect of a variation
(2) The effect of a unilateral variation
(3) The moderation of commercial difficulties of variation
3. Waiver (I)—Terminology
A. Historic Difficulties in Defining the Term
B. Definition
(1) The process of exclusion
(2) The process of inclusion
C. Provisos to a Definition
(1) Historical origins
(2) Current usage
4. Waiver (II)—Types of Waiver and Their Elements
A. Waiver by Election
(1) Elements of waiver by election
(2) Examples of waiver by election
B. Pure Waiver
C. Total Waiver
D. Unilateral Waiver
E. Equitable Forbearance
F. Elements Common to All Forms of Waiver
G. Practical Effect
5. Waiver (III)—Complexities
A. The Effect of Waiver
B. Is Waiver Case Specific?
C. The Evidence Required to Support a Waiver
D. Waiver by X’s Agent
E. Effect on Third Party Rights
(1) Title
(2) Other rights
6. Election, Affirmation, and Acquiescence
A. Introduction
B. Election
(1) Elements of the doctrine
(2) Limits of the doctrine
C. Acquiescence
7. Estoppels—A General Introduction
A. Introduction
B. The Unified Theory
(1) Formulations of the unified theory
(2) Theoretical bases for the unified theory
(3) Authority in support of a unified theory
C. The Failure of the Unified Theory
(1) The impossibility of a completely unified theory
(2) Difficulties with a unified theory limited to estoppel
(3) Rejection of the unified theory—authorities
D. The Various Estoppels—A Summary
(1) Outline
(2) General nature of the doctrines
(3) Elements
8. Equitable Forbearance
A. Introduction
(1) Background
(2) Summary of elements
(3) Terminology and approach
(4) Interface with contract
B. Elements of Equitable Forbearance
(1) Pre-existing legal relationship
(2) Promise or representation
(3) The promise must have been intended to affect the legal relationship between the
parties
(4) The promisor must have intended the promise to be acted upon or have known that it
was acted upon
(5) The promisor’s knowledge
(6) Reliance
(7) Detriment and inequity
(8) Relief
C. Scope of Equitable Forbearance
D. Effect of Equitable Forbearance on Third Parties
(1) Assignment of the contract
(2) Transfer of land
E. Formality
9. Estoppel by Representation
A. Introduction
(1) Summary of elements
(2) A rule of evidence or substantive law: may estoppel by representation give rise to a
cause of action?
(3) Estoppel by representation and contractual estoppel
(4) Mutuality
B. Elements of Estoppel by Representation
(1) Representation
(2) Knowledge and intention
(3) Reliance
(4) Detriment
C. Relief
(1) Can estoppel by representation operate pro tanto?
D. Defences
(1) The representation was improperly induced
(2) Undermining the effect of a statute
E. Effect of Estoppel by Representation on Third Parties
(1) Passing title
(2) Transferring the benefit of the estoppel
(3) Transferring the burden of the estoppel
F. Estoppel by Negligence
(1) Elements
(2) Points of difficulty
(3) An alternative explanation of the so-called ‘estoppel by negligence’ cases
10. Estoppel by Convention
A. Introduction
B. A Broader Analysis of the Doctrine
C. Application of the Doctrine
(1) Shared assumption
(2) Unjust or unconscionable
D. Estoppel by Convention as a Sword
11. Proprietary Estoppel
A. Introduction
(1) Summary of elements
(2) Terminology
B. Categories of Cases
(1) The ‘imperfect gift’ cases
(2) The ‘common expectation’ cases
(3) The ‘unilateral mistake’ cases
C. Elements
(1) Assurance
(2) Reliance
(3) Detriment
D. Remedies
(1) The aim of the discretion
(2) Exercising the discretion: relevant factors
(3) Exercising the discretion: quantum
(4) Examples of remedies granted
E. Effect of Proprietary Estoppel on Third Parties
(1) The burden
(2) The benefit
