To keep the series fresh the producers would regularly move Frank Marker around the UK. The show was originally based in London's Clapham district, moving to Handsworth in Birmingham, Brighton, Windsor, Walton-on-Thames and finally Chertsey.

Most of the ABC Television episodes (Series 1-3) are lost, while the Thames Television episodes survive intact. The only ABC episodes to survive are Public Eye: Nobody Kills Santa Claus (1965), Public Eye: The Morning Wasn't So Hot (1965), Public Eye: Don't Forget You're Mine (1966), Public Eye: Works with Chess, Not with Life (1966) and Public Eye: The Bromsgrove Venus (1968)

The phone number for Frank's Clapham office is given as MACauley 2810. Helen Mortimer (and thus Frank)'s address in series 4 was 24 Sussex Close, Brighton (tel: 851957). Marker's Windsor premises were found at: 93 High Street, Eton, Windsor (tel: 68319 or 67818) - he lived at 3 Willow Court. The office he shared in the final series was: Ronald Gash & Associates, 22a Walton Shopping Precinct (tel: 21109). He then took over the former Apollo Aerials premises adjacent to Chertsey train station, tel: 2499, with digs in Westbury Street.

The central character was originally to be called Frank Marvin, but the name was generally disliked. It was lead actor Alfred Burke who amended it to Frank Marker.

First seen in Public Eye: Well-There Was This Girl, You See... (1971), the framed artwork given to Frank by Nell Holdsworth which decorates his offices thereafter, is an 1823 representation by John George Murray (after James Stephanoff), of 'The Trial of Queen Caroline', when the Pains and Penalties Bill 1820 was pushed through and passed in the House of Lords at the bequest of King George IV in an attempt to discredit his estranged wife. Its title is fully "View of the interior of the House of Lords, during the important investigation in 1820."

Frank is given a display case of 15 pinned butterflies by a grateful client as part-payment for his fee. He has this in his Birmingham office and takes it to his short-lived Brighton premises. It then hangs in his Windsor home (as seen in Public Eye: The Beater and the Game (1971)) before being displayed in his High Street office in Public Eye: John VII. Verse 24 (1971). This is a nice piece of visual continuity although the box does actually differ slightly between the ABC and Thames episodes.

In the early years of the Thames-produced series, some shows are in colour and some are in B/W. The B&W ones were produced during 'the colour strike' when TV technicians switched off the colour during a union dispute.

Building used as Frank's office in Eton - 93 High Street, Eton, Windsor - still exists.

In Brighton, Frank is briefly allied to Joe Ryland's team of inquiry agents.

Even though it was written into the scripts that Frank Marker didn't get along with the police and vice versa, occasionally this particular status quo was altered slightly. During the episodes when Frank was based in Windsor, he and a police officer named D.I Firbanks managed to tolerate each other quite well and had a mutual respect.

Before "Public Eye," Alfred Burke had been a fairly regularly employed supporting actor in films and TV.

In a sense, the character of Frank Marker could resemble that of Philip Marlowe. Like Marlowe, Marker had dealings with clients whose morals were questionable at best. Most of them refused to pay Marker his fee or they vanished from the scene as soon as it was convenient.

Martin Shaw made an early TV appearance on the "Public Eye" series.

At the close of the third season, Marker is arrested for receiving stolen jewellery via a crooked solicitor; after pleading guilty he is sentenced to two years, six months imprisonment. Serving a year before his paroled release to Brighton, Frank (prisoner 759413) was sent to Category B/C Winson Green prison (now HMP Birmingham), transferring to the open Category D HMP Ford in West Sussex six months before his release.