6.5 17th-century Navigation
6.55 Nobody's Friend
7.20 Mendelssohn's Dream
7.45 Porphyry Copper Deposits

World Snooker
The Embassy
World Professional Snooker Championship from the Crucible Theatre, Sheffield
Twelfth day
The Quarter-finals
DAVID ICKE introduces coverage of one of the most important days of the entire championship.
The first quarter-final is played to a finish this morning and STEVE DAVIS (seeded No 1) was the hottest favourite to reach the semi-finals. On the other table RAY REARDON (2) and KIRK STEVENS (7) were seeded to continue their match.
At 2.30 DAVID VINE introduces Snooker Break with facts, figures, features and frames, and talks with some of the personalities at the Crucible.
At 3.0 another quarter-final is played to a finish and Canada's CLIFF THORBURN (2) and Australia's EDDIE CHARLTON (6) were seeded to battle for the last frames. Next door ALEX HIGGINS (5) and TONY KNOWLES (4) could be contesting an all-Northern duel as this match continues. Commentators TED LOWE
JACK KARNEHM , CLIVE EVERTON Racing from Ascot
The first flat meeting of the year from this famous course.
2.0 The Autobar Stakes (Old mile)

Only about 100 children of school age in Britain suffer from receptive aphasia-a language disorder. How does the education system cope with such a specialised problem? And what can school do to help these pupils more?
Producer NICK BRENTON
A BBC/Open University production

with subtitles, followed by Weather

Boom
A United Nations film that looks wryly look at the follies of our atomic age.

starring Fred MacMurray
Dorothy Malone , Walter Brennan When Jack Wright , a peaceful store owner, accidentally kills a bank robber, the man's brother vows revenge. The townspeople - who have regarded Jack as a hero - abandon him to his fate. But a climactic gunfight brings them to their senses ...
Screenplay by DANIEL B. ULLMAN
Produced by VINCENT M. FENNELLY
Directed by ALFRED WERKER. Films: page 14

By Arthur Ransome.
The last of four parts dramatised by Michael Robson.
PC Tedder decides to arrest the 'Death and Glory' boys, but can Dick's clever idea obtain the vital evidence in time?

The Embassy World Professional Snooker Championship from the Crucible Theatre, Sheffield Two of the semi-finalists are already known. Tonight two more will qualify. Will one of them be ALEX HIGGINS ? Can RAY REARDON put a disappointing season behind him? Will TONY KNOWLES and KIRK STEVENS reach the semi-finals for a second time in their careers? DAVID VINE introduces live coverage of one of tonight's quarter-final nine-frame sessions.

This week Jonathan King visits the island of Puerto Rico.
He takes a look at Americans on holiday, salsa music, and top Hispanic recording stars Menudo.
Plus a review of the latest pop videos and new movies.
Executive producer MICHAEL HURLL Producer GORDON ELSBURY

by JULIE WELCH
'Welcome to Paralysis Palace, Mr Cannon , the place where they make you feel four foot tall.'
Following the accident, Bob is determined to put a brave face on matters. Frank soon teaches him otherwise.
Script editor DAVID SNODIN Designer GRAEME THOMSON Producer BRENDA REID
Director MARTIN THURLEY

The International Garden Festival
Today Her Majesty The Queen opened Britain's first International Garden Festival, set in a new riverside park on the banks of the Mersey.
A severely derelict stretch of land has been transformed in less than two years into the setting for the largest event of its kind since the Festival of Britain in 1951. Chris Kelly and Peter Seabrook introduce highlights of THE QUEEN'S visit and look at the international exhibits, theme gardens and the floral displays in the Festival Hall and International Pavilions.
Producer LAURENCE VULLIAMY
• FEATURE: page 68

Starring Jack Klugman as Joey Crown

A musician with a drink problem goes on a binge that could bring his problems to an end - permanently!

12.5 Computing: Simplex Method
Solving linear programming problems by the Simplex Method means some movement between vertices along boundaries, a region denned by given constraints.
12.30 Inquiry: Colour
Colour vision depends on the object, its immediate surroundings, the illumination, but above all, on the brain behind the eye.