[17] That susceptibility of more than one meaning may, however, be able to be resolved by reference to evidence of the surrounding circumstances.[3] Without further evidence of what took place between the parties leading up to the issue of this policy it is not entirely clear to what extent matters occurring during the course of prior negotiations between Medical Plumbing and an insurance agent, Atkinson, established objective background facts known to AMP; in particular, the nature of the business actually being carried on by Medical Plumbing. However it seems likely that Mr Thornton, on behalf of Medical Plumbing, during the course of discussions with Mr Atkinson, described Medical Plumbing's business, looking at its business card, as "specialising in the Installation, Maintenance and Servicing of Medical and Industrial Gases". And in the proposal for the policy, which Mr and Mrs Thornton signed at the request of and in the presence of Mr Atkinson, they described the business as "installation, maintenance and service of medical and industrial gases". It therefore seems likely, but by no means certain, that by the time the policy was issued, the nature of Medical Plumbing's business, in those terms, was a fact known to both parties.