Nottingham Forest, one of Britain’s and the world’s oldest football clubs, marked 150 years since their Victorian formation and first match in 1866 with a game this month between two teams of supporters who had written evocative recollections of their own first matches. Peering into the immediate future for the club, however, is a murkier exercise than a nostalgic look over their distinguished past, illuminated forever by the miraculous European Cup wins of 1979 and 1980 under the managerial partnership of Brian Clough and Peter Taylor.

Forest’s owner, the Kuwaiti businessman Fawaz al-Hasawi, who has advanced loans of £67m in only four years of ownership but steered the club to 16th in the Championship last season, has for weeks been in talks to sell a majority stake to Evangelos Marinakis, the owner of the Greek champions Olympiakos.

The promise is that a magnate seasoned in success elsewhere in Europe can bring his experience to bear on reviving Forest out of these withering years. The appointments last month of Pedro Pereira, who was at Fiorentina last season, as director of football and the former Rennes and Real Sociedad manager Philippe Montanier as head coach are said by some to be signs of Marinakis’s influence already, although the club has not confirmed that.

Yet the questions over this proposed sale, which is understood to be close to conclusion, could hardly be more urgent. Marinakis is currently banned from involvement in any football administration in Greece, and the subject of a major criminal prosecution, in which he is accused of seeking to control Greek football by criminal means, including bribery and blackmail.

Marinakis was named as a key target in a 173-page report by the Athens prosecutor last April, which alleged that he sought with others “to absolutely control Greek football’s fate by the methods of blackmailing and fraud”. More than a year on he remains charged with five criminal offences, including being involved in blowing up a bakery owned by a referee, Petros Konstantineas, now an MP for the ruling Syriza party. The prosecution, which follows the previous Koriopolis match-fixing scandal in which Marinakis is understood to have been cleared, is said to be due for a verdict soon. Marinakis denies any wrongdoing.

As part of bail conditions imposed last June Marinakis reportedly paid a €200,000 bond and was handed a ban from taking an active role in Olympiakos or Greek football, which is still in force pending the conclusion of the criminal case.

One of the many remarkable features of this prospect – that a man facing criminal and corruption charges on such a scale is Hasawi’s chosen new owner for a legendary club such as Forest – is that the Football League rules may actually allow it. The owners’ and directors’ test, which determines who is “fit and proper” to own 30% or more of a club or be a director, bars people who have been convicted of a criminal offence involving dishonesty or who have been banned from involvement in sports administration by a governing or professional body.

In recent years, as the money gushing into clubs promoted to the Premier League has multiplied into a bonanza unparalleled elsewhere in sport or business, investors have taken over Championship clubs speculating to reap that windfall and the Football League has been subjected to the increasing use of lawyers to argue clubs’ cases intensely.

The City Ground in Nottingham. Photograph: Shaun Botterill/Getty Images

The owners’ and directors’ test was taken to the finest interpretation of its wording by lawyers for the Leeds United owner, Massimo Cellino, in 2014, who ultimately defeated the Football League’s argument that Cellino was barred due to his conviction in Italy for tax evasion. His lawyers’ case, which the barrister presiding over the hearing, Tim Kerr QC, allowed, was that Cellino’s criminal offence, at that stage, might not have involved dishonesty.

Within months written reasons for the conviction were delivered in Italy which did find Cellino had been dishonest, and he was barred by the League, but by then the Italian was fully installed as the owner at Elland Road and he returned as a director after his conviction was spent.

At present Marinakis has not been convicted of a criminal offence, only accused of five serious ones. He is not, apparently, banned from involvement in Greek football by the Hellenic Football Federation or other governing body, or by a professional body, but as a bail condition. The League, which has declined to comment as it has sought from Forest further details of the prospective takeover, has been poring over its test’s precise wording to see if Marinakis, in a situation never envisaged when the rules were introduced in 2004, is caught by it.

Hasawi had hoped to be the owner-investor who would return Forest to the Premier League which, including the bloated parachute payments which ease a drop back to the Championship, now delivers £200m to a club for a single season as a member. However, for the £67m loaned by his family, stated in Forest’s most recently published accounts, Hasawi’s record incorporates a trail of unsuccessful managers, sundry unpleasant episodes including the banning of journalists, and a transfer embargo last season under the Football League’s financial fair play rules due to excessive losses. Forest’s accounts show that the club made a £21.5m loss in the year to 31 May 2015, following £24m lost in 2013-14.

Having spent so heavily without reward and losing the faith of many supporters in his ability to restore Forest to prosperity, Hasawi was open to new investment and, of all potential buyers, came up with Marinakis. Representatives of Marinakis, asked via Forest about the criminal investigation and proposed investment, declined to comment.

A spokesman for Forest said: “The club will not be providing an official response on any potential individuals who may be investing in the club. However, the club can assure all supporters that any potential investment will be carried out with the full approval from all relevant governing bodies, to ensure the best outcome for Nottingham Forest.”

Richard Antcliff, interim chairman of the recently formed Nottingham Forest supporters’ trust, said the club did need a change and revival from their current disappointments, but he is concerned about the Marinakis prospect. “We want our club to be successful again, in a sustainable way,” Antcliff said. “We want to believe positive change is on the horizon but it is worrying to see an individual with this kind of baggage. We would like some very early reassurance that the club is in safe hands.”