The most recent al-Jazeera documentary on spot-fixing in cricket is to be welcomed but it remains a source of frustration as well. The scope to manipulate a game of cricket for betting purposes has been with us for two centuries or more and any reminder of that is a useful deterrent. But we crave more hard facts than the “unsupported allegations” referred to by David Leatherdale, the chief executive of the Professional Cricketers’ Association who confirmed on Monday “the [English] players refute all allegations and have the full support of the PCA”.

This latest documentary expands on “the Munawar Files” and alleges how Aleem Munawar, a fixer based in India whose whereabouts are unknown, has been able to arrange patterns of play in international matches to allow surefire betting success for his clients. Generally this involves batsmen going surprisingly slowly during a given period of play, usually of 10 overs. As a consequence there is now the depressing possibility that whenever we catch a batsman removing his helmet or stopping the bowler running up to the wicket he may, in fact, be signalling the fix is on.

In the programme we see Munawar photographed in the vicinity of some of the world’s greatest cricketers during the World T20 tournament in Sri Lanka in 2012, which should never be taken as evidence of implicating those cricketers. Perhaps these pictures serve another purpose: they are likely to impress Munawar’s potential clients.

It is easy to be convinced from the footage that Munawar has been blithely culpable of trying to corrupt the game of cricket and many of the world’s top cricketers in the process. The allegations are that those involved in spot-fixing include some prominent England cricketers and several examples, but no names, are cited, some of which relate to what is supposed to be the saintliest form, Test cricket: among the matches highlighted are three Tests in the Pakistan v England series in the United Arab Emirates in 2011 and an England v India Test at Lord’s in 2012.

The frustrations lie with the fact that Munawar is clearly eager to impress his would-be client – al-Jazeera’s undercover investigator, David Harrison – with the scope and range of his powers over the world’s international cricketers. Moreover every time we seem to be getting to the nitty-gritty, the names of those claimed to be conniving with the spot-fixers are withheld. At some point the makers of such programmes have to put up or shut up. They have to do more than pinpoint those who are engaged in spot-fixing off the field.

Both the England and Wales Cricket Board and Cricket Australia have issued strong statements supporting their players and the hope is that their confidence is totally justified. But it is not necessary to be a conspiracy theorist to be uneasy about some of these claims. In 2000 the immediate reaction of this correspondent to allegations of Hansie Cronje fixing elements of cricket matches was a naive “I can’t believe he would ever sink to this.” Since then the stain of fixing has never been eradicated and the necessity to keep an open mind has become ever greater. As Munawar says in the programme: “With enough money, you can do anything.” It surely behoves al-Jazeera to hand over all of its evidence to the International Cricket Council as well as to Interpol.

In some ways the first of the two al-Jazeera programmes, which appeared in May, is of more immediate relevance to England’s cricketers in Sri Lanka. In that programme there are allegations of how bribes were offered and accepted to fix the pitch in Galle, the venue of the first Test in England’s Test tour, which begins on 6 November. Against India in 2017 it is alleged a hard, true surface was summoned up by the fixers to ensure some mighty run‑scoring – Virat Kohli’s side racked up 600 in their first innings – while a spinner’s paradise was ordered for the 2016 game against Australia, a match that ended within three days.

Whether the fixers have been in operation or not before England’s match – and one assumes the al-Jazeera programmes have, at least, reduced that possibility – we can anticipate England’s players would prefer to see a surface more favourable to batsmen than spin bowlers when they arrive there in a fortnight’s time; for purely cricketing reasons the Sri Lankans may take the alternative view. More importantly the hope remains that the nature of the pitch in Galle has not already been decided by fixers.