13.1 Omission, failure or delay on the part of any Party to exercise any right, power or privilege under this Agreement, shall not operate as a waiver thereof; nor shall any single or partial exercise of any right, power or privilege preclude its further exercise or the exercise of any other right, power or privilege. No waiver by a Party shall be valid unless it is made in writing and specifying the breach or circumstances the subject of the waiver and such waiver shall only apply to such breach or circumstances and not to any other breach or circumstances.
13.2 An amendment to this Agreement shall not be effective unless it is made in writing and signed by both Parties hereto.
13.3 If any provision of this Agreement is or is held to be invalid or unenforceable by a court of law or other competent governmental authority for any reason, then so far as it is invalid or unenforceable it has no effect and is deemed not to be included in this Agreement. This shall not invalidate any of the remaining provisions of this Agreement. The Parties shall then use all reasonable endeavours to replace the invalid or unenforceable provision by a valid provision the effect of which is as close as possible to the intended effect of the invalid or unenforceable provision.
13.4 Each of the Parties shall pay its own legal and accountancy costs, charges and expenses (including taxation) incurred in connection with negotiating and preparing this Agreement and the transactions contemplated by it.