“ include the terms on which the services are provided, having regard to the terms of the contracts forming part of the arrangements under which the services are provided." 73. The National Insurance provisions are in theSocial Security Contributions (Intermediaries) Regulations 2000 made undersection 4A Social Security Contributions and Benefits Act 1992 and provide that, on conditions which, for the most part, are the same as those in the corresponding provisions of ITEPA, an amount calculated by reference to the receipts of the intermediary is to be treated as paid by the intermediary to the worker as employment earnings. 74. The difference, however, lies in the words of the third condition - paragraph (c) - and in the absence of any equivalent to section 49(4). The relevant NI regulation reads: This Part applies where– (a) an individual (“the worker") personally performs, or is under an obligation personally to perform, services for another person (“the client"), (b) the performance of those services by the worker is carried out, not under a contract directly between the client and the worker, but under arrangements involving an intermediary, and (c) the circumstances are such that, had the arrangements taken the form of a contract between the worker and the client, the worker would be regarded for the purposes of Parts I to V of the Contributions and Benefits Act as employed in employed earner’s employment by the client. 75. In Dragonfly v HMRC[2008] EWHC 2013 (Ch) Henderson J held that there was a (regrettable) potential difference in the effect of these differing provisions. He said: “For whatever reason, the NIC test requires the arrangements themselves to be embodied in a notional contract, and then asks whether the circumstances (undefined) are such that the worker would be regarded as employed; whereas the income tax test directs attention in the first instance to the services provided by the worker for the client, and then asks whether the circumstances (widely defined in paragraph 1(4) in terms which include, but are not confined to, the terms of the contracts forming part of the arrangements) are such that, if the services were provided under a contract directly between the client and the worker, the worker would be regarded as an employee of the client. Nine times out of ten, perhaps ninety-nine times out of a hundred, the two tests will lead to the same answer. However, it cannot necessarily be assumed that this will always be the case.” “…I will also say that, if a choice were to be made between the two systems, I would regard the income tax approach as preferable. The problem with the NIC approach is that the "arrangements involving an intermediary" referred to in regulation 6(1)(b) cannot always be reformulated or collapsed into a notional contract between the worker and the client without a good deal of remoulding and evaluation of the surrounding circumstances, especially where (as in the present case) there is another party involved (such as DPP) and the arrangements include a chain of contracts with possibly conflicting provisions. In other words, the remoulding of the arrangements into a single notional contract will probably involve in practice very much the same process as the more open-textured income tax test expressly envisages” 76. Neither part suggested to me that this difference should make any difference in this appeal. 77. Thus I am required to determine whether the circumstances of Mr Mantides’ engagements with RBH and MMH were such that if his services were provided under a hypothetical contract between him and the relevant hospital, Mr Mantides would be regarded as an employee. All the circumstances including the arrangements with the intermediary are to be taken into account, and may affect both the terms of the hypothetical contract and whether it would give rise to an employment relationship. Employment – Case Law 78. In MKM Computing Ltd v HMRC SpC00653 I set out the principles which I derived from the authorities in relation to whether or not a person was employed. In this appeal the parties referred me to a number of other and more recent authorities. I set out below the principles I derived in MKM with additional references to those authorities. 79. (i) There is an irreducible minimum for a contract of employment. That minimum was described in Ready Mixed Concrete v Minister of Pensions and National Insurance(1967) 2 QB 497 , where MacKenna J set out three necessary conditions for a contract of services: “(i) [the mutuality test] The servant agrees that in consideration of a wage or other remuneration, he will provide his own work in the performance of some service for his master; (ii) [the control test] He agrees, expressly or impliedly, that in the performance of that service he will be subject to the other’s control in a sufficient degree to make that other master; (iii) [the inconsistency test] the other provisions of the contract are consistent with its being a contract of service.” 80. These tests are a good starting point when considering whether a contract is one of employment and it is important that mutual obligation and control are identified before moving on to consider other factors (see Buckley J at paragraph 23 in Montgomery v Johnson Underwood Ltd(2001) EWCA Civ 318 ). Whilst the tests are necessary conditions for employment the nature and extent of the requirements for mutuality and control are not rigid but depend upon the circumstances. MacKenna J’s third condition has to my mind much in common with the overall picture and in-business-on-his-own-account tests I describe below and the use of various indicia. The mutuality test and the control test require some further comment. (ii) The Mutuality Test . 81. There are two aspects to this test: first that there must some mutuality of obligation, second that the contract must be for “his own work” – for the worker’s personal service. That second aspect gives rise to the question as to whether a right for the taxpayer to substitute another person in his place can prevent a contract being one for service. I discuss that under Substitution below. 82. In relation to the question of mutuality of obligation I concluded in MKM : (i) For there to be an employment contract there must be a contract. That requires some mutual obligations: an obligation on the one hand to work and on the other to remunerate. (ii) A contract cannot be an employment contract unless the `employee’ is obliged to provide his labour. (iii) An obligation on the employer to provide work or in the absence of available work to pay is not a precondition for the contract being one of employment, but its presence in some form (such as for example an obligation to use reasonable endeavours to provide work, to allocate work fairly, or not to remove the ability to work e.g. by removing the pupil to be taught) is a touchstone or a feature one would expect to find in an employment contract and whose absence would call into question the existence of such a relationship. 83. The parties referred me to a number of employment law cases which dealt with a worker who works intermittently for the same employer. In such cases if it is found that there is an umbrella contract for a longer period which is punctuated by shorter periods of work, it may be then found that a period of continuous employment with the same employer is established for the purpose of certain employment law remedies. 84. The authorities indicate that for such an umbrella contract to remain in force there must be some minimum mutual obligation which continues during the breaks in work engagements, but "whilst the fact that there is no umbrella contract does not preclude the worker being employed under a contract of employment when actually carrying out an engagement, the fact that a worker only works casually and intermittently for an employer may, depending on the facts, justify an influence that when he or she does work it is to provide services as an independent contractor rather than as an employee." and the absence of mutuality outside the period of work may shed light on the character of the relationship within it: it could indicate a degree of independence incompatible with employee status ( Secretary of State v Windle[2016] EWCA Civ 459 , per Underhill LJ at [14 and 23] approving what had been said in Quaishi . 85. Mr Mantides referred me to Clark v Oxfordshire. This concerned "bank nurses" available to be called on to work in a casual capacity to fill a temporary vacancy. The appellant worked intermittently for a hospital authority for three years and claimed continuous employment during that period for the purposes of an unfair dismissal action. Sir Christopher Slade in the Court of Appeal said that no "umbrella" contract could exist "in the absence of mutual obligations subsisting over the entire duration of the relevant period". The lower tribunal had found that there was no mutuality (no obligation to offer or accept work) in the period in which the nurse did not work, and as a result the Court of Appeal held that there was no umbrella contract. 86. But I do not consider that this case offers much assistance in relation to the question of whether each separate engagement was an employment because at the end of its judgement the Court allowed the possibility that each separate engagement could be an employment (and remitted the appeal back to the tribunal to decide that point). 87. I was also referred to McMeechan v Secretary of State for Employment1997 ICR 549 . There, Waite LJ said that when considering the terms of an individual self contained engagement the fact that the parties were not obliged in future to offer or accept another engagement was neither here nor there. 88. I conclude that the lack of any obligation to provide work after the end of a fixed term contract does not mean that there is insufficient mutuality of obligation during the term, and in the context of such an engagement it is but a weak pointer away from employment. 89. These cases did not affect my former conclusion (see above) that in relation to a particular engagement an obligation on the employer to provide work or in the absence of available work to pay was not a precondition for the contract being one of employment, but its presence in some form is a touchstone or a feature one would expect to find in an employment contract and whose absence would call into question the existence of such a relationship (iii) Substitution. 90. The contract must be for personal service. Nevertheless a limited or occasional power of delegation or right to substitute another person may be consistent with a contract of personal service. ( Usetech : paras 49-52). 91. Mr Mantides referred me to Primary Path v HMRC [2011]. There the tribunal summarised conclusion in Dragonfly v HMRC[2008] EWHC 2013 (Ch) as being that if there is a general and unqualified right for the worker to send along a substitute, that is incompatible with employment, and that determines the matter; something less than that is unlikely to be determinative but a contract which has at least some recognition that a substitute can be supplied must "seriously be considered" as not being employment [68 and 69]. I agree and would add that the more qualified that right the less serious is its effect on the overall picture. (iv) Control. 92. MacKenna J’s control condition was “control in a sufficient degree to make that other the master”