From Compact Oxford English Dictionary

spontaneous

• adjective 1 performed or occurring as a result of an unpremeditated impulse and without external stimulus. 2 open, natural, and uninhibited. 3 (of a process or event) occurring without apparent external cause. 4 Biology (of movement or activity) instinctive or involuntary.


I think an English court would look to an English dictionary rather than the American Websters. So if it is planned in advance it won't be spontaneous.