Stephen Mogridge aka Jill Stevens

British author, mainly of mystery and adventure type novels. His most popular books were probably the New Forest series, in which some of the characters had their own ponies. I don't think that they featured in any of his other adventures but if anyone knows to the contrary please let me know!

Also writes under the psuedonym of Jill Stevens. These tended to be aimed more at girls whereas the other books were aimed at both sexes.

New Forest Series:
Adventure/mystery series. A group of children have many adventures in the New Forest, some with their ponies, others without. I have not read them all so I don't know the extent of pony content in them all.

Lots more on the series here

1) NEW FOREST ADVENTURE
(NELSON 1953)
ILLUSTRATED BY WINSLADE
Reprinted in paperback in 1960 as part of the Nelson Juniors imprint.

2) NEW FOREST MYSTERY
(NELSON 1954)
ILLUSTRATED BY WINSLADE

3) NEW FOREST QUEST
(NELSON 1955)
ILLUSTRATED BY WINSLADE

4) NEW FOREST EXPLOITS
(NELSON 1956)
ILLUSTRATED BY ROBERT HODGSON

5) NEW FOREST DISCOVERIES
(NELSON 1957)
ILLUSTRATED BY ROBERT HODGSON
Reprinted in paperback in 1959 as part of the Nelson Juniors imprint.

6) NEW FOREST SMUGGLERS
(NELSON 1958)
ILLUSTRATED BY ROBERT HODGSON

7) NEW FOREST PIRATES
(NELSON 1959)
ILLUSTRATED BY ROBERT HODGSON

8) NEW FOREST VAGABONDS
(NELSON 1960)
ILLUSTRATED BY ROBERT HODGSON
Rare

9) NEW FOREST DETECTIVES
(NELSON 1962)
ILLUSTRATED BY ROBERT HODGSON
Quite rare

10) NEW FOREST TREASURE
(NELSON 1963)
ILLUSTRATED BY ROBERT HODGSON
Rare.

11) NEW FOREST SPIES
(NELSON 1964)
ILLUSTRATED BY DRAKE BROOKSHAW
Quite rare

Collectors info:
Only a couple of these were reprinted as paperbacks.
New Forest Exploits and Discoveries are the easiest ones of the series to find. Most of the others, whilst not common, can be tracked down on the internet without too much bother. The last 4 however are much rarer and may be quite expensive to buy.

As Jill Stevens:

JANE'S LONELY DONKEY
(NELSON 1958)
ILLUSTRATED BY DICK HART
Reprinted in hardback by Nelson.
SUMMARY: Paula and Jane were good friends, so two were Paula's pony Sunspot and Jane's donkey Percy. Percy did not want to be separated from his friend so when Paula exercised Sunspot he had to come too! Soon Paula is beginning to wonder if she can extricate herself from the donkey without hurting her friends feelings...

Collectors info:
Although not common, it is still reasonable easy to find on the internet.