What should I do if I'm ill and will miss an academic commitment?
If you cannot fulfil your compulsory academic commitments because you have a problem (normally illness) beyond your control, then the most important thing to do is to inform your college as soon as possible and complete a Self-Certification of Absence form (available from your college). You should submit this form to the college Student Support office, who will pass the relevant information to the Department, where the appropriate members of staff will be notified automatically.
Normally you do not need to contact the Department separately, unless your illness/absence has a direct effect on summatively-assessed work, in which case you should contact the member of staff responsible for administering the deadline as soon as possible. In the case of weekly problems or weekly assessment of laboratory performance, there is no need to contact the Department to apply for a deadline extension, since these cannot normally be granted, but instead you will be excused the week's assessment simply on the basis of your Self-Certification of Absence form (assuming the reason is valid). It should be noted that if you miss a laboratory session without submitting a Self-Certification form to your college at the time of absence, your "laboratory performance" mark may suffer.
These procedures are explained in more detail, together with information about long-term medical conditions and medical evidence, at http://www.dur.ac.uk/physics/students/deadlines/ and http://www.dur.ac.uk/physics/students/medical/ and the deadlines notices (including the names of the staff members responsible for administering the deadlines) are available on the notice boards and in pdf at the above URL.
If you believe in advance that you will be unable to fulfil an academic commitment (for reasons beyond your control, such as a funeral or a hospital appointment) then it is your responsibility to plan ahead and attempt to make suitable arrangements with the Department, such as finding out whether there is an alternative class that you could attend. You should then indicate such arrangements on your Self-Certification form.
Job interviews, family weddings, etc. do not count as "reasons beyond your control" and therefore the Self-Certification form is not appropriate. See https://www.dur.ac.uk/physics/students/faqs/?faqno=3189 for guidance in such cases. For requests relating specifically to University sport see https://www.dur.ac.uk/physics/students/faqs/?faqno=1267.