Inclusion Criteria:

1. The subject is able to read and understand the Informed Consent Form (ICF), and understand study procedures.
2. The subject has signed the ICF.
3. Healthy male or female subjects aged 55-64 years inclusive. Attempts will be made to achieve an equal gender ratio through appropriate screening procedures, but a failure to do so will not preclude analysis of the final data set.

4. The subject has a history of the following sleep characteristics during the past three months or more at Visit 1:

   • Bedtime between 22:00-00:00h on at least five nights per week
   • Reported typical nightly sleep duration between 6.5 and 8.5 h
   • The subject has a regular sleep-wake cycle and maintains a regular sleep-wake cycle during the study
5. The subject is a non-smoker who has not used nicotine or nicotine-containing products for at least approximately 6 months. Subjects who have discontinued smoking or the use of nicotine/nicotine containing products for at least approximately 3 months may be enrolled in the study at the discretion of the investigator.
6. The subject is, in the opinion of the investigator, healthy on the basis of a physical examination, medical history, vital signs, ECG, and the results of routine laboratory tests.

Exclusion Criteria:

1. The subject is female AND of childbearing potential. Female volunteers will be considered not of child-bearing potential if they are:

   1. Pre-menopausal women who have been surgically sterilized by bilateral oopherectomy and/or hysterectomy, OR

   2. Post-menopausal, defined as:

      • No spontaneous menstruation for at least one year prior to the first dose,
      • Follicular stimulation hormone (FSH) >18mIU/mL, AND
      • Not lactating.
2. The subject has a known sensitivity to temazepam, zolpidem or melatonin or a history of any allergy that in the opinion of the investigator would contraindicate subject participation.
3. The subject has a BMI of less than 19, or more than 33kg/m or a total body weight of less than 50 kilograms at pre-study (screening) visit. BMI is calculated by taking the subject's weight in kg and dividing by the subject's height in metres, squared.
4. The subject has a score of >5 points on the Pittsburgh Sleep Quality Index (PSQI) scale.
5. The subject has a history of clinically significant sleep pathology according to DSM-IV TRTM or presents symptoms of clinically significant sleep pathology at PSG screening. AHI of >10 and PLMAI of >10.
6. The subject is a shift worker or maintains an irregular sleep-wake schedule during 1 month preceding the screening visit, or travelled within the last month preceding the screening visit and/or during the study to a time zone more than 2 hours different to the current time zone in Surrey.
7. The subject consumes more than three (men) or two (women) units of alcohol per day on average over the 1 month preceding Visit 1(screening visit) [NOTE: 1 unit is equivalent to a half-pint (220mL) of beer or 1 (25mL) measure of spirits or 1 glass (125mL) of wine].
8. The subject consumes more than 5 caffeine-containing beverages per day.
9. Clinically significant psychiatric, cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrine, neurological (particularly myasthenia gravis), immunological, or haematological disease or abnormality, as determined by the study physician.
10. History of alcohol, narcotic, benzodiazepine, or other substance abuse or dependence within the 12 months preceding Visit 1.
11. Positive urine drug screen at any visit at Surrey CRC (i.e., amphetamines, barbiturates, benzodiazepines, cannabinoids, cocaine, or opiates). A repeat test will not be allowed.
12. Positive alcohol breath test at any visit to Surrey CRC. A repeat test will not be allowed. [NOTE: subjects must be told to avoid consumption of alcoholic beverages for at least 24 hours prior to attending the Centre].
13. Use of any psychotropic medications such as benzodiazepines, barbiturates and narcotics, or other medications, including over the counter (OTC) and herbal products including melatonin that may affect sleep/wake function, within the 3 months or 5 half-lives preceding Visit 1, whichever is longer, or a need to use any of these medications during the study.
14. Use of any other medication which may interfere with study outcome and/or interfere with IMP within the 2 weeks or 5 half lives preceding Visit 2, with the exception of non-steroidal analgesics, and paracetamol. [NOTE: Concomitant medications which do not influence study outcome and/or do not interfere with IMP may be allowed at the discretion of the investigator].
15. Hereditary problems of galactose intolerance, the Lapp lactase deficiency, or glucose-galactose malabsorption.
16. Currently participating in another clinical trial with an investigational or non-investigational drug or device, or has participated in another clinical trial within the 3 months preceding Visit 1 (screening visit).
17. Concomitant use of HRT by female volunteer.
18. Any condition that, in the investigator's opinion, compromises the volunteer's ability to meet protocol requirements or to complete the study.
19. Subject must be able to refrain from strenuous or unaccustomed exercise such as weight lifting, running and bicycling 24 hours before visits 2, 3, 4, 5 and 6, and 24 hours after visits 2, 3, 4, 5, and 6.