Shepherd, 70, left the Magpies in 2007 and is estimated to be worth around £75m.
His return to football has come as he is one of the men reportedly helping a bid for the Glasgow side being fronted by Charles Green.
Shepherd is now part of the Triple S Sports and Entertainment Group along with his football agent son, Kenneth, and Paul Stretford, the agent who represents Manchester United’s Wayne Rooney.
An unconditional offer from former Sheffield United chief executive Green has been accepted by administrators.
Shepherd has connections with the Glasgow club, and brough chief executive Freddy Fletcher (also pictured) to St James' Park from Ibrox in 1992.
Fletcher, along with then-chairman John Hall, re-shaped the club and the stadium and turned it into what we know now.
FOLLOW EURO 2012 WITH NEWCASTLEUTD-MAD
EURO 2012
Group A
Poland
Greece
Russia
Czech Republic
Group B
Holland
Denmark
Germany
Portugal
Group C
Spain
Italy
Republic of Ireland
Croatia
Group D
Ukraine
Sweden
France
England
EURO 2012 FINALS MATCH SCHEDULE
All match kick-off times are BST.
GROUP STAGES
Friday June 8
Warsaw, Group A: Poland v Greece (1700)
Wroclaw, Group A: Russia v Czech Republic (1945)
Saturday June 9
Kharkiv, Group B: Holland v Denmark (1700)
Lviv, Group B: Germany v Portugal (1945)
Sunday June 10
Gdansk, Group C: Spain v Italy (1700)
Poznan, Group C: Republic of Ireland v Croatia (1945)
Monday June 11
Donetsk, Group D: France v England (1700)
Kiev, Group D: Ukraine v Sweden (1945)
Tuesday June 12
Wroclaw, Group A: Greece v Czech Republic (1700)
Warsaw, Group A: Poland v Russia (1945)
Wednesday June 13
Lviv, Group B: Denmark v Portugal (1700)
Kharkiv, Group B: Holland v Germany (1945)
Thursday June 14
Poznan, Group C: Italy v Croatia (1700)
Gdansk, Group C: Spain v Republic of Ireland (1945)
Friday June 15
Donetsk, Group D: Ukraine v France (1700)
Kiev, Group D: Sweden v England (1945)
Saturday June 16
Wroclaw, Group A: Czech Republic v Poland (1945)
Warsaw, Group A: Greece v Russia (1945)
Sunday June 17
Kharkiv, Group B: Portugal v Holland (1945)
Lviv, Group B: Denmark v Germany (1945)
Monday June 18
Gdansk, Group C: Croatia v Spain (1945)
Poznan, Group C: Italy v Republic of Ireland (1945)
Tuesday June 19
Donetsk, Group D: England v Ukraine (1945)
Kiev, Group D: Sweden v France (1945)
QUARTER-FINALS
Thursday June 21
Warsaw, QF1: Winner A v Runner-up B (1945)
Friday June 22
Gdansk, QF2: Winner B v Runner-up A (1945)
Saturday June 23
Donetsk, QF3: Winner C v Runner-up D (1945)
Sunday June 24
Kiev, QF4: Winner D v Runner-up C (1945)
SEMI-FINALS
Wednesday June 27
Donetsk, SF1: Winner QF1 v Winner QF3 (1945)
Thursday June 28
Warsaw, SF2: Winner QF2 v Winner QF4 (1945)
FINAL
Sunday July 1
Kiev: Winner SF1 v Winner SF2 (1945)