before embarking upon a detailed description of the embodiments , it is to be understood that the element protector control of fig1 and 2 is a modified form of the x1 control aforementioned which is described in gb - a - 2194099 with particular reference to fig3 a , 3b and 3c thereof . reference should be had to gb - a - 2194099 for a full understanding of all aspects and advantages of the subject control which will be described only briefly in the following . referring first to fig1 the element protector control illustrated therein comprises first and second moulded plastics body parts 1 and 2 which are adapted to fit together and to capture therebetween first and second terminals 3 and 4 and spring metal conductors 5 , 6 and 7 . on the other side of body part 2 there is provided a bimetallic primary switch actuator 8 which , in similar manner to the x1 control described in gb - a - 2194099 , is adapted to be mounted in a plastics material carrier 9 which is adapted in turn to locate in predetermined manner with the front ( not visible ) face of body part 2 . the bimetallic primary switch actuator 8 is arranged , in a manner substantially identical to that described in gb - a - 2194099 , to determine the status of a switch defined by the parts 10 and 11 of the spring metal conductors 5 and 6 , a push - rod 12 being provided for this purpose . the parts 10 and 11 normally make electrical contact with each other and are opened by push - rod 12 when the bimetallic primary switch - actuator 8 responds , in use , to an element overtemperature condition . in the event that the primary switch actuator fails , for whatever reason , to open the contact between the parts 10 and 11 , the heating element will continue to be powered so that its temperature will rise to a level whereat the secondary thermally - responsive actuator constituted by the plastics material carrier 9 will become operative . the carrier 9 has rearwardly - facing projections 13 and 14 which are designed to extend through the body part 2 and into contact with the parts 15 and 16 of the spring metal conductors 5 and 7 so that , when the control is operatively coupled to a planar heating element and the carrier 9 is urged rearwardly towards the body part 2 , the spring metal parts 15 and 16 are urged by the projections 13 and 14 into contact with the terminals 3 and 4 respectively . the carrier 9 has four legs 17 with feet 18 which sit upon the rear surface of an associated heating element and , when the element temperature rises to such a level as to cause the legs 17 to begin to melt , the carrier 9 is collapsed in a forwards direction towards the heating element by the spring action of the conductor parts 15 and 16 so that the conductor parts 15 and 16 eventually move out of contact with the terminals 3 and 4 of the control . the element protector control of fig1 and 2 is adapted for use with a generally planar heating element and it will be seen that the spring metal conductors 6 and 7 have forwardly extending portions 19 and 20 which are adapted to project forwardly of the control body part 2 and make electrical contact with terminal portions of the planar heating element for supplying electrical energy thereto through the control . referring now to fig3 a and 3b , these show sectional side elevation and schematic plan views respectively of an exemplary form of planar heating element in accordance with one aspect of the present invention . the planar heating element comprises a stainless steel substrate or base plate 20 having an electrically - insulating first layer 21 of glass formed thereon in a central area thereof , a heater track 22 formed of electrically conductive ink formed on the glass layer 21 , and an electrically - insulating second glass layer 23 formed over the heater track 22 and over the first glass layer 21 . an opening or window 24 is provided in the second glass layer 23 so as to expose the heater track 22 beneath the opening and , as shown in fig3 b , the opening 24 is sized to enable the bimetallic primary actuator 8 of the control of fig1 to be directly responsive to the temperature of the heater track 22 , but to locate the feet 18 of the carrier 9 on the glass surface outside of and surrounding the opening . additional openings 25 and 26 are provided in the second glass layer 23 at locations corresponding to terminal ends 27 and 28 of the heater track 22 and are arranged to be contacted by the forwardly projecting parts 19 and 20 of the control spring conductors 6 and 7 when the control is fitted in operative relationship with the heating element . the terminal ends 27 and 28 of the heater track 22 are preferably formed of silver or of a likewise good electrical contact material . mounting pillars 29 and 30 are provided on the heating element base plate 20 for enabling the attachment of the element protector control thereto . such mounting pillars may be screw threaded or may be designed to be engaged by any suitable form of friction securing means . in operation of the thus - described planar heating element with the thus - described element protector control , the fact that the bimetallic primary actuator of the control is in direct heat transfer relationship with the heater track of the element ensures a rapid response of the control to an element overtemperature situation . at the same time , by insulating the secondary protection means , namely the collapsible carrier 9 , from the heater track 22 , it is ensured that the thermal overshoot which normally accompanies the primary operation of the control , that is to say the dynamic temperature rise that normally occurs in the element after operation of the primary protection , will not result in actuation of the secondary protection . the close thermal contact of the bimetallic primary actuator with the heater track furthermore enables improved primary protection response times to be achieved which additionally reduces the temperature overshoot level . these factors facilitate the selection of appropriate materials for the carrier 9 . the relatively &# 34 ; flat &# 34 ; shape of the element protector control is furthermore aesthetically advantageous and simplifies the task of incorporating the control into an aesthetically pleasing appliance design . there has thus been described in the foregoing an arrangement of a bimetal control with a deforming backup protection , mounted to a printed element , in which the bimetal of the control makes direct thermal contact with the heater track and the deformable backup protection is thermally insulated from the track by an outer layer of glass which limits the overshoot temperature to which it is exposed , so that practical thermoplastics may be used in its construction . in addition , in this arrangement , a construction is described in which electrical connection to the heater track is made by direct contact between springs , which are integral with the control , and printed contact points electrically connected to the heater track . the invention having thus been described with reference to exemplary embodiments , it is to be clearly understood that the described embodiments illustrate and exemplify the invention and do not limit the same , and that modifications and variations will occur to those possessed of relevant skills without departure from the scope of the invention as indicated by the appended claims . for example , an enclosure may be provided on the opposite ( wet ) side of the planar element at a location corresponding to the location of the opening 24 whereat the bimetal 8 senses the element temperature , the enclosure having apertured walls permitting the ingress of water into the enclosure when the vessel is filled , but of such a size and arrangement that when water boils in the vessel the generation of steam in the enclosure expels the water therefrom . by virtue of the provision of such an enclosure , a single control serves both as an element overtemperature control operating to switch off the element if , for whatever reason , it overheats , and also to switch off the element automatically when water boils in the vessel , the boiling of the water in the vessel and the expulsion of water from the enclosure causing an element overtemperature condition within the enclosure which causes the control to operate .