“63 … in accordance with the referring court's own findings, the use by H3G, in the advertisement in question, of bubble images similar to the bubbles trade marks did not give rise to a likelihood of confusion on the part of consumers. The advertisement, as a whole, was not misleading and, in particular, did not suggest that there was any form of commercial link between O2 and O2 (UK) on the one hand, and H3G, on the other. 64 In that regard, contrary to the submission of O2 and O2 (UK), the referring court was right to limit its analysis to the context in which the sign similar to the bubbles trade marks was used by H3G, for the purpose of assessing the existence of a likelihood of confusion. 65 It is true that the notion of likelihood of confusion is the same in Articles 4(1)(b) and 5(1)(b) of Directive 89/104 (see, to that effect,Case C-425/98 Marca Mode[2000] ECR I-4861 , paragraphs 25 to 28). 66. Article 4(1)(b) of Directive 89/104, however, concerns the application for registration of a mark. Once a mark has been registered its proprietor has the right to use it as he sees fit so that, for the purposes of assessing whether the application for registration falls within the ground for refusal laid down in that provision, it is necessary to ascertain whether there is a likelihood of confusion with the opponent's earlier mark in all the circumstances in which the mark applied for might be used if it were to be registered. 67. By contrast, in the case provided for in Article 5(1)(b) of Directive 89/104, the third-party user of a sign identical with, or similar to, a registered mark does not assert any trade mark rights over that sign but is using it on an ad hoc basis. In those circumstances, in order to assess whether the proprietor of the registered mark is entitled to oppose that specific use, the assessment must be limited to the circumstances characterising that use, without there being any need to investigate whether another use of the same sign in different circumstances would also be likely to give rise to a likelihood of confusion.”