1 Complicated puzzle invented by Erno (6,4)
6 Abbreviation seen on bottles of port, brandy, etc (4)
10 In Greek mythology, a sea nymph supposed to lure sailors to destruction (5)
11 A conspicuous constellation in the southern hemisphere near the Southern Cross (9)
12 Niccolo ---, Italian violinist and composer who died in 1840 (8)
13 Roman market place (5)
15 Large edible marine gastropod of the genus Heliotis having an ear-shaped shell with pearly interior (7)
17 French city which was the home of a number of Popes (7)
18 Geoffrey ---, author of The Canterbury Tales (7)
20 Continent, north and south (7)
21 Organic compound formed by reaction between an acid and an alcohol with elimination of water (5)
22 Former province in NW France (8)
25 Naval battle in 1805 off the SW coast of Spain (9)
26 A religious meal shared as a sign of love and fellowship (5)
27 Town on the Isle of Wight (4)
28 The second wife of Henry VIII of England and mother of Elizabeth I (4,6)

1 Coarse file with sharp pointed projections (4)
2 English romantic novelist who published her first book, Jigsaw, in 1921 (7,8)
3 Marsupial friend of Winnie the Pooh (5)
4 Addictive narcotic obtained from coca leaves (7)
5 Portuguese football team, winners of the European Cup in 1961 and 1962 (7)
7 English buccaneer and explorer whose ship was the Golden Hind (3,7,5)
8 Letter delivery man in the village of Greendale (7,3)
9 Measure of the rate of disintegration of the radioactivity of a substance (4-4)
14 Large city in north-west England (10)
16 The ---, cow enclosure in Tombstone, Arizona, scene of a gunfight in 1881 (2,6)
19 Wilhelm ---, German physicist and discoverer of x-rays [alt. spelling] (7)
20 Lanarkshire town (7)
23 Besieged by Mexican forces, 1836 (5)
24 Cryptogamous vascular plant (4)