The Dartline was unveiled by Duple at the 1988 British International Motor Show in Birmingham, along with the Dennis Dart chassis.

[1][2] Initially offered in just one length, 9 metres, its most distinctive feature was its curved, asymmetric windscreen covering the destination sign with an arched top.

[7][8] Of the 22 C27-coded 9.8-metre versions, eight were ordered by London Country North West and delivered after that company's takeover by Luton & District, while the remaining 14 went to numerous small operators.

[10] Carlyle closed in early 1992, and the rights to all of its designs, including the Dartline, passed to Marshall Bus.

In late 1993, Marshall redesigned the Dartline as the C37, with a symmetrical windscreen and a more substantial front bumper.