You probably think that I've got to say this after my rash 4-0 prediction at the start of the series, but I still think that England can win this series against South Africa. That is even despite the fact that the momentum in this series seems to have swayed decisively towards the home team.

But my confidence comes with two important warnings: that England will only win the series if two men can suddenly find their form- namely skipper Michael Vaughan and fast bowler Steve Harmison. They have both been poor so far in this series. They know that, and we know that. But why is a very much more difficult question to answer.

The leader has always been targeted by all opposing captains, and Vaughan has had to deal with this before. But what is most worrying now is that his poor batting record has become a trend while skipper.

The figures before and after being handed the captaincy do not make pleasant reading. They seem to show that the burdens of leadership are affecting him, and unless he can sort matters out soon the pressures on him will only increase until they become intolerable.

This may all seem rather strange to be even discussing this when one considers the year England have just enjoyed, but it is an undeniable truth of international cricket that a team cannot hold an under-performing captain for too long.

For short periods, yes. But over the extended period, no. Remember that the skipper is an all-rounder- a batsman and a tactician- and that all-rounders who are underachieving in one facet of the game do not last too long in the team. Sooner or later they are replaced.

Vaughan needs runs, as simple as that. And I think he will get them. He is far too good a player not to, and I know for a fact that he has been working feverishly to rectify any problems in his technique while the team has had a break after the exhausting back-to-back Tests in Durban and Cape Town.

Recently, because he has been on edge and eager to get bat on ball, his trigger movements (those he makes before the ball is delivered) have got out of sync, with an extra one creeping in which gives the impression that he is not moving his feet.

He is experiencing the age-old dilemma for a batsman out of form -- whether to blast a way out of it or graft through it. I tried both on numerous occasions and am still not sure which is best. Both worked at various times for me.

Vaughan was clearly favouring the positive option when he hooked to deep square leg in the second innings at Cape Town, and look at the stick he has received for that. Because of that he may now go into block mode. I'd prefer it if he was positive -- that is when he plays best.

Harmison's difficulties are more difficult to unravel. There have been suggestions he is homesick, something he has suffered badly from in the past. But that would be surprising since his family have been with him for most of the tour.

I am no expert on bowling actions, but there would seem to be little different in his bowling action from the one which gave him so much success last year. So what is it? I think it may be the way the South Africans have played him.

They are very good leavers of the ball - especially Jacques Kallis- and I think this has disconcerted Harmison and made him try different things. He needs to be as patient as the batsman and not lose that individual battle of attrition. England desperately need him to come good again.

Which leaves us with our own Simon Jones. He has certainly been the topic of conversation, some of it complimentary, some of it not. A certain G Boycott seems to have it in for him, but he is not the only victim there.

I think he's bowling really well, probably as well as I have seen him for a long time. His accuracy has improved beyond all recognition, and there were signs in Cape Town that his speed is beginning to crank itself up again- a few times passing the 90mph mark, of which he is readily capable.

He was definitely under-bowled in the last Test. Why I don't know, and I certainly hope the rumours about Jimmy Anderson coming into replace him today do not come true. That would not be the solution. Vaughan and Harmison coming good is the remedy.