“30. … the guiding principle in an application to adjourn of this type is whether if the trial goes ahead it will be fair in all the circumstances; that the assessment of what is fair is a fact-sensitive one, and not one to be judged by the mechanistic application of any particular checklist; that although the inability of a party himself to attend trial through illness will almost always be a highly material consideration, it is artificial to seek to draw a sharp distinction between that case and the unavailability of a witness; and that the significance to be attached to the inability of an important witness to attend through illness will vary from case to case, but that it will usually be material, and may be decisive. And if the refusal of an adjournment would make the resulting trial unfair, an adjournment should ordinarily be granted, regardless of inconvenience to the other party or other court users, unless this were outweighed by injustice to the other party that could not be compensated for.”