Conditional bonds and guarantees depend on the terms of the bond or guarantee, as well as the terms of the underlying contract. A surety can argue that it has no liability under the bond or guarantee where the parties to the underlying contract vary it. As a result in English law, conditional bonds and guarantees should contain an 'indulgence' clause, which expressly allows the parties to the underlying contract to vary the contract or the works or the time for paying for those works. This note sets out some of the pitfalls for the unwary. The note was developed by Sarah Fox, author of the 500-Word Contract. As a solicitor she was an expert in bonds and guarantees on construction projects, learning a great deal about how to draft, negotiate and call on them. For help writing simpler contracts, including 500-word bonds or understanding complex ones, all other bonds and guarantees, email: sarah@500words.co.uk or visit www.500words.co.uk

1. Indulgence Clauses in Guarantees and Conditional Bonds
Conditional bonds and guarantees are ubiquitous on UK construction projects. They are a specialised
form of contract, which provide another person (the surety) with a liability which matches that of
the contractor or subcontractor.
In legal terms, they provide secondary liability – this means that the liability of the surety is
dependent on and the same as the liability of the contractor under the guaranteed contract. The
surety’s liability is neither longer nor deeper!
But, because the surety’s liability is dependent on the terms of a contract to which it is not a party,
the general rule is that the original contract cannot be varied without the surety’s consent. To do so
may change its liability and prejudice its position:
“It is a well-established principle that any variation in the terms of the underlying agreement
which could prejudice the position of a guarantor will, unless his consent is sought and given or
unless the contract expressly provides to the contrary, discharge him from all liability. The
authorities establish that it is immaterial that the variation has not in fact prejudiced the
guarantor or that the likelihood of its so doing is remote. Provided the variation could prejudice
the guarantor, the nature of the risk undertaken has been altered and he is the person entitled to
decide if the guarantee is to be continued notwithstanding that change. This principle has been
consistently and strictly applied by the English Courts”1
Any material variation or alteration of the principal contract, without the surety’s consent, is
sufficient to discharge the surety from further obligations under the guarantee: Holme v Brunskill,2
as upheld by the Court of Appeal in Triodos Bank NV v Dobbs.3
The issue of variation was reviewed by the Court of Appeal in Hackney Empire v Aviva,4 in which
Lord Sugar makes a cameo appearance.
The rule in Holme v Brunskill has the effect of requiring the employer to obtain the prior consent of
the surety to any variation of the obligations that have been guaranteed or of other matters which
might affect the rights of the surety and the risk it has undertaken.
If the employer does not seek consent, then the surety will defend any claim on the bond or
guarantee. The employer may be able to argue that such a defence is not available if it is ‘selfevident’ that either the amendment could only be beneficial to the surety or that its effect was
insubstantial to the risks undertaken by the surety.5 These are high hurdles to overcome!
What Can Discharge the Surety?
Whether there has been actual prejudice or detriment is not relevant. It is judged objectively – a
merest whiff of ‘not insubstantial’ detriment, or a variation which may or may not be detrimental to
the surety, is sufficient. So what do you need to look out for?
The answers may come as something of a surprise, because, without the ‘no variation clause’ which
occurs in the majority of bonds and guarantees, the surety can be discharged from liability for
myriad reasons:
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Variation of the works themselves – variations under a contract as expressly provided for do not
discharge the surety;6
Void principal contract – where the guarantee provides secondary liability, if the principal
contract is void or unenforceable in its entirety, then there is no liability to secure and the surety
is discharged;7

2. 
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Novation by operation of the law – this does not discharge the surety, see Maritza;8
Forbearance or waiver – this discharges the surety, see Nisbet v Smith (1789)9 where the
employer gave the debtor further time for payment; and also Associated British Ports v
Ferryways10: ‘it has long been held that even the shortest extension of time [to pay] will
discharge the surety’;
Settlement of disputes – this may discharge surety, as will the rescheduling of debts, see e.g.
Marubeni Hong Kong & South China Limited v The Mongolian Government;11
Replacement of original principal contract with second contract – will discharge the surety,
Triodos Bank v Dobbs, if not within the scope of the original agreement;
Surrender of other security or of another surety – discharges the surety;12
Absolute release of the principal debtor – discharges the surety;13
Non-repudiatory breach of contract – will not discharge the surety, although an accepted
repudiatory breach will.14
Conclusion
As the court does not find it easy to ‘draw a hard and fast line between permissible and
impermissible variations’,15 then you need to ensure that any conditional bond or guarantee does
contain an indulgence clause.
The Author
Sarah Fox of Enjoy Legal Learning wrote this note. She is a speaker and trainer who cuts through the
complexities of construction law. She provides confidence to construction companies to read, use
and understand their contracts. She is also author of the 500 Word Contract™.
To find out how Sarah can help you love your terms and conditions, contact her on: 07767 342747 or
by email: sarah@enjoylegallearning.co.uk
Footnotes
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Mr Colin Reese QC in Oval (717) v Aegon Insurance Limited 85 BLR 997. Emphasis of the court.
(1877) 3 QBD 495.
[2005] EWCA Civ 630. This case concerned the extent to which a surety was bound by subsequent agreements.
[2010] EWHC 2378. As at July 2012 this case was going to Appeal.
See e.g. The Wardens and Commonality of the Mystery of Mercers of the City of London v New Hampshire
Insurance Co Ltd, cited above, where a short delay in possession was not sufficient to discharge the surety as the
surety had been unaware at the time of granting the bond what the date of possession would be. See also
Marubeni & Hong Kong, cited below.
Stewart v McKean (1855).
See e.g. dicta of Eveleigh LJ in Potton Homes Ltd v Coleman Contractors Ltd (1984) 28 BLR 19 (CA), where he
considered alternative defences apart from the fraud exception for on-demand bonds. “If the contract is avoided
or is there is a failure of consideration between the buyer and seller for which the seller undertook to procure
the issue of the performance bond, I do not see why, as between the seller and buyer, the seller should not be
unable to prevent a call upon the bond.”
AES-3C Maritza v Credit Agricole [2011] EWHC 123 (TCC).
29 ER 317; (1789) 2 Bro CC 579.
[2008] EWHC 1265 (Comm), appealed on different grounds.
[2004] EWHC 472 (Comm).
E.g. Smith v Wood [1929] 1 Ch 14.
Commercial Bank of Tasmania v Jones, PC, [1893] AC 313.
National Westminster v Riley [1986] BLCL 268.
Paragraph 17, Longmore LJ in Triodos Bank v Dobbs, above.