(to 7.20)

Why is grass green? This programme looks at the events leading from the selection of visible wavelengths of light to the perception of colour.
A BBC/Open University production

The Topper sailing dinghy was the first to be built of the plastic polypropylene. The design team looks back over how the boat evolved.
A BBC/Open University production

A See-Saw programme
(R)

The size of telephone exchanges is a problem. It is possible to connect every telephone subscriber with every other subscriber directly, but this is inefficient. Optimisation is necessary.
A BBC/Open University production

from Tidmarsh, Berkshire with Geoff Hamilton and Roy Lancaster

Regional News and Weather

from the Manor House Hotel, Mortonhampstead
Today Peter Alliss 's guest is Dan Maskell who talks about his life in tennis. (R)

Isobel Ward and Simon Barnes present this magazine Programme for and about disabled people and their families. Included this month is a report on why a group of disabled YTS trainees was sent to the Lake District, and a discussion about the sheltered employment of disabled people.
There's news of the launch of a new employment and training fund, and a report on some useful gadgets for use in the home. There's also a chance to enter a lyric-writing competition. Producer CHRISTOPHER HUTCHINS 0 INFO: page 77

A Castle on the Map
Twenty-five years ago Harry and Deirdre Margary were looking for a home, and happened upon Lympne
Castle in Kent. Whether it was the ghosts, or the view, or the Roman ruin, they fell in love with it - and the castle in turn changed their lives.
Strangers insisted on looking round the castle - so the Margarys had to open it to the public, write a guide book, and produce tea and scones.
Executive producer JENNIFER JEREMY Director SANDRA WAINWRIGHT (R)

Joan Bakewell Meets Simon Dee
Twenty years ago a young disc-jockey called Simon Dee was given his own show on BBC Television. He achieved instant fame, and his show captured the flavour of the 60s. A few years later Dee's career was over, when he became as suddenly unfashionable as the miniskirt. In this second of four programmes based on extracts from the last series of Did You See... ?,
Joan Bakewell invites Simon Dee back to the BBC to remember his heyday.
Director DEVENDRA VARMA Producer CHARLES MILLER (Revised repeat)
(Tomorrow: Inside the Six O'Clock News)

In two years, No Limits has built an audience of millions who consider it the best music TV show in the world, so it was no surprise that thousands of teenagers applied to host the series.
Hundreds asked us to keep
Jenny Powell and Tony Baker around so they will be guiding 16 co-hosts - two from each of the eight BBC regions - through the next six months. Tonight 124 finalists are whittled down, so check out some of the brightest young faces in Britain, the greatest music in the world and No
Limits inventor - J.K. himself. Associate producer JONATHAN KING Production PETER HAMILTON BBC North West
0 BACK PAGES: 86

1: Bring 'Em to Task
In 1824 the RSPCA was formed to combat the dreadful cruelty inflicted on animals. In the 1980s cases of cruelty are increasing yearly. This six-part series follows Chief Inspector Sid Jenkins and his team as they carry out methodical investigations. Executive producer ROGER MILLS Producer PAUL BERRIFF

Presented by Chris Kelly Could you recognise six different types offish, or decorate a sponge with cream and fresh fruit in under 90 seconds? Could you identify four wines ideal for the summer, just by sniffing and tasting them; or devise two sandwich fillings from a mystery set of ingredients, and prepare them in under two minutes? These are just some of the challenges which Chris Kelly sets the teams. Doing battle are resident cooks Michael Barry and Michael Smith drinks experts Jill Goolden and Oz Clarke with this week's special guests actress Nanette Newman and former England cricket captain Bob Willis
Will they know Mrs Beeton 's Christian name? (Answer below)
Producer JEREMY MILLS
Series producer PETER BAZALGETTE
0 FEATURE: page 85
* CEEFAX SUBTITLES

Tomorrow's Victims
'Parents in Fear', 'Doctors in Dilemma' say the headlines. The 'Cleveland Calamity' has thrown into sharp relief the tensions between parents and professionals in coping with the sensitive area of the sexual abuse of children. Last week Brass Tacks suggested that a more positive approach to the abusers themselves might bring a significant drop in the number of offences. Tonight, parents, professionals, former victims, and you the viewers who rang in response to last week's film, join
John Harrison in the Brass Tacks studio to argue through the effective ways of protecting children - and preventing the victims of tomorrow.
Studio director ROBERT KHODADAD Producers
CLAIRE LEWIS. MALCOLM BETNEY Editor COLIN CAMERON BBC North West

starring
Dick Powell
Claire Trevor
Chandler's great creation, Philip Marlowe , authentically portrayed by Dick Powell - world-weary but not cynical. Here the tough private eye is asked by the simple-minded 'Moose' Malloy to find his former girlfriend Velma. The search involves him in a lot of trouble, several murders, a terrifying drug
'trip' and plenty of gun-play, before the complicated story is finally resolved.
Screenplay by JOHN PAXTON Based on the novel by RAYMOND CHANDLER
Produced by ADRIAN SCOTT
Directed by EDWARD DMYTRYK
(The RKO Story - Tales from
Hollywood - is shown on Friday at
9.35*pm)
0 IN THE PICTURE: page 16
* CEEFAX SUBTITLES

The last word on world events analysed by Peter Snow
Donald MacCormick and Adam Raphael with political and economic reports from Vincent Hanna Will Hutton and Nick Clarke

What gives rise to pressure in gases? Pucks, ball-bearings and polystyrene provide some of the answers in this programme on 'Discovering Physics'.
(R)
(to 0.30)