  Identifying the population of young stellar objects (YSOs) in high extinction
regions is a prerequisite for studies of star formation. This task is not
trivial, as reddened background objects can be indistinguishable from YSOs in
near-infrared colour-colour diagrams. Here we combine deep JHK photometry with
J- and K-band lightcurves, obtained with UKIRT/WFCAM, to explore the YSO
population in the dark cloud IC1396W. We demonstrate that a colour-variability
criterion can provide useful constraints on the star forming activity in
embedded regions. For IC1396W we find that a near-infrared colour analysis
alone vastly overestimates the number of YSOs. In total, the globule probably
harbours not more than ten YSOs, among them a system of two young stars
embedded in a small (~10000 AU) reflection nebula. This translates into a star
forming efficiency SFE of ~1%, which is low compared with nearby more massive
star forming regions, but similar to less massive globules. We confirm that
IC1396W is likely associated with the IC1396 HII region. One possible
explanation for the low SFE is the relatively large distance to the ionizing
O-star in the central part of IC1396. Serendipitously, our variability campaign
yields two new eclipsing binaries, and eight periodic variables, most of them
with the characteristics of contact binaries.
